It has been observed and regretted by a well-known writer, that “a periodical work resembles a public carriage—which must depart at the usual hour, whether full or empty;”—and having undertaken to deliver this work at stated periods, I have found myself in a situation not unsimilar: the consequence of which has been a too cursory view of some of the subjects. I feel however, that this is not a sufficient apology for any essential defect: nor would it be more so to say that, although verging to old age, I am still a young author. Yet I may claim the privilege of supplying, in the latter parts of the work, what is most deficient in the former; and thus of proving that I do not intentionally neglect any thing that might make it practically useful.

With these views I commence this third part: intending first to continue the description of the Cutting Engine given at page 121, and here applied to Bevil Wheels; and then to re-consider, shortly, one or two other objects, that were too rapidly passed over in their proper places.

Plate 22, repeats at fig. 1, the first figure of Plate 15; by way of shewing the additions required to extend this method of cutting teeth, to Bevil Wheels. These additions are first, a disk n n, concentrically fixed to the main axis A B of the engine. And, second, an inclined plane o, of variable obliquity, connected by a joint with the forked sliding bar p q, by which the plane o is put in contact with the disk, at whatever distance the cutter-stand e f may be from the common centre, which distance depends, of course, on the diameter of the wheel to be cut; and to secure which is the office of the fixing screw r, in the figure.

It is now evident that for the disk n n, and the shaft A B to rise, the slide p q and the cutter-stand e f must recede: and this more or less according to the degree of obliquity of the inclined plane o, that is according to the slope of the bottom of the teeth in the wheel w: see the dotted line w p.

A circumstance presents itself, that should be here explained: when the bevil of the wheel w, or the cone of which the wheel is a part, is very obtuse, the cutter-stand e f, can not be driven back by the action of the disk n n on the plane o, without too great a stress being applied from below, to the axis A B. (See the apparatus I M O N, Plate 16, fig. 2.) In this case therefore, the handle R is not used: but a weight is suspended to the end N of the lever M N, sufficient to give the whole System A B, a tendency to rise; and the operator now acts on the screw g, so as to draw back the plane o; by which motion the disk m n with it’s axis A B is suffered to move upward, and the wheel is cut, as desired. But on the other hand when the wheels are portions of acute cones, they are cut by means of the aforesaid handle; by which the plane o and the cutter-stand are forced backward as before intimated.

We proceed now to describe the perpendicular part of the cutter stand e f; which is made double, as shewn at i k in fig. 4 of Plate 15; and is also perforated at various heights to receive the bolt which forms the centre of motion of the arm m u, the latter having a cylindrical boss u, fitted into the fork of the stand e f, and so graduated as to determine the angle of it’s obliquity to the horizon, or it’s parallelism to the dotted line w p, which indicates the slope of the bottom of the teeth on the wheel. Finally, the cutter-frame x is fastened to this arm at right angles to it, and thus forms a right angle (or nearly so) with the surface of the wheel: and is, moreover, directed to the centre, produced, of the shaft A B. This latter fact is strictly true, only when the teeth required are of so common a kind as not to require greater exactness: for in theory the sides of the cutter (supposed cylindrical) must alternately direct to that centre—namely, that side which is actually cutting: so that a provision must be made to shift the cutter spindle sideways, a distance equal to it’s diameter; this being no more than what is necessary in every system of wheel cutting.

We may also consider here, the form of the cutter itself, v, fig. 1. It is slightly conical, (more or less so according to it’s use) and of no greater diameter than the smallest width of the spaces between the teeth of the wheel. A common disk-like cutter would not produce perfect, nor even tolerable teeth on a bevil wheel. The reason of this will appear by considering that a spiral line, either on a cone or it’s base, turns more the further it is from the centre, and less the nearer it comes to it. So that a flat cutter placed at any angle, is parallel to the curve at one place only; whence the propriety of using a cutter of the kind represented in this figure. It is however true, that the first opening of the spaces may be made with a common cutter; but it should be very thin comparatively with the spaces required: and it’s cut would serve only as a sketch of such space, serving principally to permit the metal to escape while finishing the teeth with the cutter just described.

I proceed now to the examination of the plates, and the manner of adapting their length to the process of cutting spiral teeth on bevil wheels. But before entering on this subject, I would explain a kind of inadvertency into which I fell at the close of my former description of this Engine (see page 129). In my zeal to be candid in stating the properties of my Machines, I have suffered it to appear that I thought this an “imperfect” one:—an expression which, although modified among the errata, may still cause it to be looked upon as radically defective; than which nothing could be further from the idea I wished to convey. I intended merely to express the want of absolute connection between the two movements of the shaft—the rotatory and longitudinal motions. I meant that the process by this Machine was not theoretically certain, because dependent on the action of a weight (Plate 16, fig. 1 and 2) and an unforced obedience to the direction of the plates. But this small remove from rigourous principle is in my opinion much overballanced by the facility of cutting good wheels of all diameters, by the sole change of a morsel of tin, which leaves untouched every other part of the Engine.

Entering then on this branch of the subject, I first observe that if we chuse for the teeth an inclination of 15 degrees (in imitation of the cylindrical wheels) it can only be for one point of such wheels—as observed above. This point therefore I have placed at r in the middle of the face. And supposing now that at this point the wheel O were 4 inches in diameter and the wheel S two inches, these plates would be found as before by these analogies:

(1) wr, or 2 inches: 11 inches (rad. of plate rim)? 26.8: ^294.8/₂ = 147.4 plate required.

(2) vr, or 1 inch: 11 inches (rad. of plate rim)? 26.8: ^294.8/₁ = 294.8 2d. plate required.

But it is plain that the conical face, b C, (common to both wheels) is broader than the supposed cylindrical ones b e and b d: and therefore that the above plates must be made longer (to furnish the said obliquity) in the following proportions, namely: for the wheel O in the ratio of b e to b C; and for the wheel s in that of b d to b C: that is, these plates should be lengthened as the tabular cosines of the angles B A C and D A C to radius (for b e: b C? A B: A C; and b d: b C? A D: A C.) Thus then,

(1) Cos. 63°27': radius? 147.4 (present plate): required plate x, = ^{147.4 r}/_{Cos. 63°27'}; and

(2) Cos. 26°33': radius? 294.8 (present plate): required plate y, = ^{294.8 r}/_{Cos. 26°33'}.

Now, by the tables, cosine 26°33' = 894, and cosine 63°27' (it’s complement) = 447, when radius is 1000: whence dividing the two equations by r, and substituting these values of cosines 63°27' and 26°33' we shall find the two quantities x and y, equal. Whence it appears that for every pair of bevil wheels, whose shafts lie at right angles, the same plate serves for both wheels: only turning it once to the right, and once to the left hand on the plate rim.

And if now we measure on a scale of equal parts, the line A r and call it 100, we shall find the line w r (near enough for practice) to be 90, and the line v r to be 45, and these numbers respectively, put for rad. for cos. 26°33', and for cos. 63°27', will make the first equation x = 147.4 × ¹⁰⁰/₄₅ and y = 294.8 × ¹⁰⁰/₉₀ or x = 327.55 and y = 327.55, &c. confirming the above deduction that the same plate serves for both wheels; and giving, withal, the length of the plate required.

In performing this operation by actual measurement of the lines, I have had in view to trace a path for those of my readers who may not have the tables, or may be unaccustomed to use them. The process, generally, is to take the diameter of any bevil wheel O fig. 4, in the middle of it’s face; and supposing it a spur wheel, to find it’s plate by the method above given: and then to multiply the length of that plate by the line A r and divide the product by the line A w, both measured on the same scale of equal parts.

It may be well to observe, likewise, that the same method of finding the plates, applies to bevil wheels of every description or angle: but that it does not give equal plates for every pair, except in the above case of wheels placed at right angles to each other.

I would just remark that by the figure near B, is shewn a section of the Machine on which I centre the wheels to be cut on this Engine. It is an inverted cup s t, into which the arbor is screwed in a true position; and this cup is fixed on the top of the shaft A B, by the three pressure screws near s t, which enter a triangular neck made round the shaft, against the upper slope of which, the screws press so as to draw the cup downward in the act of centering it. This I say is my present method; but it is in a measure accidental, the shaft not having been perforated to receive arbors of the usual kind. Mine, however, have their utility in the ease with which they are varied in size, and changed on the Machine: but on their comparative usefulness I give no opinion. The other is the most solid method.

In the description of my differential Steel-yard, (see page 163) I stated that the load P was wholly collected in the point o; and that dividing the line A C by the line A o, the power of the Machine was known. But I should have shewn that this line (A o) is equal to one half the difference between the arms A D and A E. To do this, here, (see Plate 23, fig. 4) I take the Machine in the state of infinite power, before mentioned; and observe, that in moving the point of suspension from o towards A, I at once lengthen the arm A E, and shorten the arm A D: by which process, (supposing each arm to have been called a) that which I lengthen by any quantity d becomes a + d, and that which I shorten by the same quantity becomes a - d, and the difference of these quantities, is 2d: so that the line A o is in reality one half the difference between the two arms A D and A E as was required to be shewn.

But we may go a step further: The two arms of the equibrachial lever x y may likewise be made unequal: and the line s a be subdivided in any ratio: which division will augment still more the power of this Machine. If for example, we hang the load on the point v, halfway between a and s, that power will be doubled; for the line c v (representing the space moved through by the load in this case) is only one half of that w s, or o q, and might be still less at pleasure. Thus the whole power of the Machine is now found by dividing the length of the long arm, beyond D, by the line a v, instead of the former line A o, or dividing the motion of it’s extremity upward, by the line c v, the motion downward, of the load P.

It has been further suggested, that the description of my excentric Bar Press was not sufficiently explicit. I have therefore added the figure 2 of Plate 22, to assist in elucidating that description. I had, perhaps made an undue use of the principle of virtual velocities by saying, too concisely, (page 174) that “as the whole approaches toward B C, the relative motion (of the cheeks s and B) becomes insensible, the circles parallel, and consequently, the power infinite.” It is however vulgarly said that power cannot be gained without losing time—which implies that if time is lost, power will be gained: and the principle of virtual velocities says the same thing, though in more appropriate terms—that if a small movement be given to a system of bodies actually counterpoising each other, the quantity of motion with which one body ascends, and the other descends perpendicularly, will be equal: so that, as remarked in page 50, by “whatever means a slow motion is obtained, dependent on that of a moving force, the power is great in the same proportion.” Now, in the eccentric Bar Press, (see fig. 2) this is so in an eminent degree: for when the bars are in the position A B, the distance of the cheeks is equal to B s; and they must move, circularly, as far as A f, to bring them closer to each other by the quantity s a: dividing therefore, the distance B g by the line s a, we find (near enough for practice) the power of the Machine within the limits A g B. It is nearly as 10 to 1. In like manner this power at A e g, is equal to the arc e g divided by the line f b; and at A l n to the arc l n divided by the line d k, namely by the difference of the lines k l and m n. From the above it appears that the nearing motion of the cheeks of the press, becomes slower and slower as the bars A and C come nearer to the point C: insomuch that the difference between the lines m n and o p is nearly imperceptible, and that between the lines o p and C q entirely so. But according to the above process, the distance p C should be divided by this imperceptible line, to find the power of the press at the point C; which therefore is immense. Another proof of this may be drawn from the supposition (see fig. 3) that the small lever a d is turned round the centre o by a bar o C fixed to it, and of equal length with the line A C fig. 2. Fig. 3 shews that the lines or bars C d, and a C are moved endwise by the circular action of the points a and d; and therefore (by statics) their motion is the same as though caused by the perpendiculars b o and o c let down from the centre o, on each of them. Hence the power of this Machine is found by dividing the distance o C by the sum of the lines b o and o c; which sum (when these lines vanish by the union of the bars over the centre) becomes infinitely small: the quotient of which division therefore is infinitely great—as was to be shewn.

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OF
A PUNCH MACHINE,
For Engravers to Calico Printers.

The usual method of making Punches for engraving Copper Cylinders, (otherwise than by the milling system) is to cut the desired pattern on a die, and then to transfer that pattern by blows or pressure to the punch, from which it is again transferred to the cylinder. My Machine in this operation, unites motion to the needful pressure; and thus renders the result more easy and complete. This effect I could the better ensure, because the surfaces of my punches are essentially convex, or rather cylindrical; as will appear when my engraving Machine comes to be described. Their convexity however, can be diminished at pleasure—whence this Machine is capable of offering useful assistance to a maker of flat punches.

In Plate 23, A B fig. 1 and 2, is the body of the Machine, with the vibrating bar C D laid upon it; reposing especially on the correct and level parts of the body at a b; this bar contains the die c, with which it vibrates between the cheeks B R, as impelled by the screws E F, it’s centre of motion being the pin P, duly supported by the strong shoulder A. In a line with the bar C D, is placed a second vibrator G, containing the steel d, that is to become a punch, already rounded into the cylindrical shape it must have when finished. This vibrator has it’s centre of motion at e fig. 1, and it need not be added that the curvature of the punch depends on it’s distance e d from that centre: for the centre of the long bar C D is so distant as to have little influence on it’s formation. Further, the cap or bridge H I, which furnishes a centre for the smaller vibrator G, can be brought forward to any useful position by the nuts K L: that cap sliding horizontally between the cheeks M N as directed by the small arms m n. This motion, then, taken from the nuts K L, serves to impress the work of the die on the steel prepared for the punch; and this being done to a first degree, both the handles O Q, are laid hold of: and by turning the screws the same way one of them goes forward and the other recedes, until the punch and die have been in contact over half their surface. At this moment both screws are turned backward, and the motions of the two vibrators reversed: by the repetition of which alternate motions accompanied by the needful pressure, the whole pattern is transferred from the die to the punch—when the latter is taken out of the Machine, and filed up in the usual method.

It should be observed, that the smaller vibrator G can be displaced with ease when the nuts K L are withdrawn: and this should be frequently done to examine the progress of the impression. Nor is there any difficulty in re-entering the figures. In a word, the perfection of this process depends more on much motion than on violent pressure: whence this facility of re-entering is a desirable property. This Machine is usually laid on a bench or tressel, with a long mortice in it, into which the feather x of this Machine enters so as to be firmly fixed.

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OF
A DIFFERENTIAL PUNCH MACHINE
For Engravers.

I was the rather induced to attend a second time to the differential Steel-yard, because I had it in contemplation to apply that principle to the present purpose; since, to make flat punches, is to some engravers a more desirable thing than to make cylindrical ones. I am not fully persuaded that it is even possible to transfer a large pattern, from a flat die to a flat punch, by any pressure acting simultaneously on the whole surface. In those cases, if there is much work, the whole surface goes down; and the parts that form the pattern do not rise. But, all that can be done in this case, is, I believe, feasible by the Machine now to be described.

Plate 23, gives in fig. 3 and 4, a representation of this Machine; A B and C D, are two slides, having wedge-formed ends above A and below D, well made, well steeled, and well tempered. One of these slides contains the die and the other the steel prepared for the punch (see B C). These wedge-ended slides are embraced by two levers E F, G H, which are themselves connected by two stirrups I K and L M, better shewn at fig. 3. These latter are supposed in fig. 4 to be broken at L M, to leave the levers E F and G H more visible. They are formed, at the turning below, into wedge-like edges a b; well hardened, that clip the nicks c d of the lower lever: and at the top of the Machine their arms e f, pass through the caps m n, above which they are nutted like a common bolt, and made to press strongly on the main lever E F. The stirrup placed to the right hand, presses in particular, by it’s cap n, on the moveable step o, exactly in the notch q: this step having a backward and forward motion communicated by the regulating screw p. Before beginning to use this Machine, I make all it’s arms A E, A g, D e, D d, equal, when it’s power (see page 162) is infinite; and to put it in a working state, I turn the screw p backward, say one half round: which motion (if the screw has 20 threads to the inch) makes a difference in the two arms A r and A q of ¹/₄₀ of an inch, and the virtual centre of the Machine is therefore ¹/₈₀ of an inch from the former point A, that is from the edge of the slide A in this fig. 3. Supposing now, the whole working lever E F to be 3 feet, and the workman’s force to be 100lbs. in each arm, then by displacing the lever to any proper distance from F towards f, he will produce a pressure between the die and the punch of 200lbs. multiplied by 1440, the number of times that ¹/₈₀ of an inch is contained in 18 inches.—That is, a pressure of two hundred and eighty-eight thousand pounds!

I have been seduced, by the anticipated brilliancy of this result, from the regular course of description,—and the plate w x, y z, which forms the base or frame of this whole Machine has not yet been spoken of. But that plate is supposed screwed down to a horizontal bench, at or near the height of a man’s breast; the slides or cases are fastened to it, and the man is supposed to work the Machine nearly as he would a die-stock in tapping a screw. This however is not indispensable; the Machine might be placed vertically, and these motions given by any proper mover; or a weight may be suspended to the arm F, so as to add continuity to pressure. It is however important, that the position should comport with the frequent extraction of the punch in order to examine the progress of the work, or cut away any redundant metal. I have before given it as my opinion that much could not be expected from mere pressure: but this is a pressure of a peculiar kind, consisting of immense powers with very short motions. In this respect it is just what was wanted, as it can be renewed and repeated frequently, without loss of time. And the more to facilitate this delicate operation, the hollow slides or cases B C, are made slightly pyramidical, to be furnished with set-screws on the four sides, by which to change the place of bearing; and thus to meet the case of a flat punch with the advantage of impressing it by portions, so as to have only to finish it by brute pressure.

The foregoing application of the principle of the differential Steel-yard, is, I think, important, and founded on unobjectionable principles; for although by changing alone the place of the step o, we disturb a little the parallelism of the stirrups I K, and L M; we do it not enough to produce, any material change in the theoretical result. With respect then to the lesser properties of this Machine, I leave them with confidence in the hands of those whom they most concern—who doubtless, will treat them with greater practical utility than I could myself hope to do.

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OF
A MACHINE
For Moulding Nails.

This Machine offers, I think, a valuable application of a well known Instrument: or rather of the principle on which it is founded. I allude to that parallel ruler which, by means of an additional joint, keeps it’s members not only parallel, but directly opposite each other. In my Machine for moulding Nails, I wanted to give motions to the two plates different, yet dependent on each other. Supposing then, (Plate 24 fig. 1, 2, 3, 4,) the upper plate a b, to be moved up and down by a lever, a screw-press, or any other first mover, I connect the under plate c d, with it by two (or four) strong parallel rulers e f, in such a manner, that when the plate a b is drawn upward it shall extend the arms of the ruler almost to a straight line, as represented in fig. 4; and then carry the under plate with it: and when it comes down again (see fig. 3) it shall not carry down the said under plate, until the same arms are bent into the position f g; that is, till the two plates touch each other: the use of which arrangement I will now explain.

The under side of the upper plate a b, is ground perfectly flat, and bored at proper distances with holes to receive and hold the punches which represent the shanks of the nails that are to be moulded. The lower plate c d is ground true both on it’s upper and under surfaces; the first to fit the under surface of the upper plate, and the under surface to impress a perfect plane on the sand below it. This under surface, shewn in an inverted position at fig. 2, is moreover covered with proper prints 1, 2, 3, &c. to form the heads of the nails in question, and with proper gets (jets?) 3, 5, 6, &c. for conducting the metal to every part of the surface. I mean models in relief of those gets; and the under plate is further pierced with holes, placed exactly like those in the upper plate, bored indeed from that (and through the aforesaid prints of the nail-heads) after the parallel joints e f have been affixed. Now on another level plate with proper ledges, the sand boxes or flasks, fig. 5 and 6, have been prepared; and have received an obtuse pyramidical form at one stroke from a competent press, the construction of which is easily conceived: or this might be done by hand, if preferred. These boxes, in-fine, are successively brought under the before described mechanism while in the state represented in fig. 3, in which all the nail models are protruded through the under plate as at 1, 2, 3. The moulder now gives a stroke under the following circumstances:—Both the plates drop together and the nail models pierce the sand while the under plate makes it’s surface perfectly level: but when that motion is reversed, it is not the under plate which first rises, but the upper—by which the nail models are drawn out of their holes without disturbing the sand, for this is kept to it’s place by the under plate: and when, by the continued motion upward of the upper plate, the parallel joints are duly extended, and the nail models quite extracted; then, and not till then, the under plate leaves the compressed sand, in which are moulded as many scores of nails as the mould has been made for—and that, in a space of time almost imperceptible.

I shall conclude the subject by observing, that the counter flask or box for closing this mould is made in the same way, by a smooth plate prepared in the same manner; and which must fit the former, because they are both perfectly level surfaces.

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OF
A FIRE ENGINE
Giving Power, while heating Rooms, Liquids, &c.

This Machine, though conceived many years ago, can hardly yet be called an invention—if material existence is necessary to justify that appellation: for I have never seen it in action. It may possibly be one of those fascinating conceptions of which my noble friend the late Earl Stanhope used to say—“’tis a beautiful invention—but ’twill not do;” yet I give it with some confidence, because of the great utility it would present, if it’s chief properties should fulfil my expectations.

The principal idea on which it is founded, is this: to use, as power, the expansion of that air which feeds the fire; and again to employ it’s heat heating liquids or rooms, or any similar purpose. The form I have given to the Machine is by no means the only one it admits; nor perhaps the best: but it was indispensable to give the idea (which I hope is not an “airy nothing”) “a local habitation and a name.”

It consists, then, of two cylinders, lying horizontally, of nearly equal length, but of unequal capacity:—one of which A B, (Plate 24, fig. 7) is an air pump with a valve in it’s end a, and another in it’s piston, both opening to the left. The second cylinder C D, is the working cylinder, as much larger than the former, as may belong to the principle of motion already announced. This cylinder receives the piston E, which fits it nicely, but is not stuffed in the present case. (It may perhaps be made tight by some of the methods, used to close metallic pistons.) At all events, this piston is connected with that c, by a frame F G H I, which embraces the whole Machine, in a horizontal position, though here shewn in a vertical. These two cylinders are cast in one piece, together with an upright cylinder, not bored K; the use of which is to receive the earthen chafing dish L M, with it’s fire, made (according to my present views) with coak or charcoal, and lighted before it is introduced. It is needless to say, that this vessel is let down into the cylinder K, by a kind of bucket handle entering any pair of holes in the dish. The top of this latter cylinder is ground to fit the flanch A N: It swings open on one of the bolts and falls to again in a moment, to prevent loss of time in firing. The means of doing this I do not much insist on, from their extreme facility. Nor do I make it a condition to use this method at all. The coak, (or perhaps the coal, or the wood) might be introduced through an upright tube furnished with two slides, one placed close above the top A N, and the other at a proper distance above; so as for one to be always shut. This is nothing more than the System used for feeding high pressure Steam Engines—only this application is to dry substances, which forms no insuperable obstacle.

When now the Machine is fired, the pistons E, and c, are pushed towards b and B respectively; the valve d having been previously opened, and the valve c opening by this very motion—which thus clears the large cylinder of it’s included air, while the air in the pump A B, is brought into contact with the fire; whence a considerable expansion ensues, and a pressure is created tending at the same time to drive the piston c to the right hand, and that E to the left: but acting in the latter case on a larger area, the whole system moves that way, and all the air in the pump A B is driven through the fire: where, being much heated, it acquires great elasticity and developes considerable power—which, by any of the known methods, may be applied to any of the known purposes.

I hope my readers will conclude here, that I allow for the disappearance of the oxigen in this conflagration: but I expect the expansion of the residue (together with what new vapour may be developed) will more than compensate for that loss of volume. By this motion then, the pump A B is again filled with cold air through the valve a; and the piston E flying out of the cylinder C D, the hot air it contained rushes into the pipe o, and thence goes to perform any heating operation that may be desired. But further, this same recession of the piston E strikes the stem of the valve d against the cover e, and opens that valve; by which means the large piston is at liberty to reach again it’s inner position b: where the bar b closes it’s valve d and prepares the Machine for a new stroke. For, as before, the pump or cylinder A B, is full of cold air, and by the backward motion of it’s piston exposes that air to the fire in K: whence arises the renewal of all the former phenomena.

Many ideas, and doubtless some objections, will present themselves to the readers of these pages; of which I shall probably anticipate some, by noticing a few less important particulars.

And first, is it not to be feared that the vertical cylinder K, and the whole system K C D E will become too hot—nay acquire a red heat, and thus introduce danger? The answer, I think, is that the fire must be lessened, or the Machine enlarged, until this danger disappears: for by heating air to any thing like a red heat (without attaining it) the expansion will be immense: and probably beyond our wants or wishes. The chaffing dish then (if that is used) must be lessened, that the air from A B may partly circulate round it, instead of going wholly through the fire: thus cooling the vertical cylinder K, and diminishing the intensity of the heat in the working cylinder. Further, the two cylinders C D and K, might be inserted in the bottom of a boiler, and surrounded with water; through which also, may be conducted the pipe O, so as to concur in the same effect of heating that water, while the steam thus accruing from the double use of this heat, may be made to drive an engine, heat a room, or fulfil any common purpose.

In a word, all our difficulties on this branch of the subject, seem to lie in excess of action: and we need only mitigate the general effect, to render this Machine useful, safe, and commodious.

There is another objection that must be met, on pain of direct censure, which is this: what will become of the ashes? (for smoke is as yet out of the question) my answer is—a recess, or several, must be found for them beyond o; to do which will not be more difficult than to lodge any other residue. But if this Machine fulfils my views in respect of power, this residue will be no burden. For example, if ever a farmer should hereafter drive his plough by such an engine as this, he will manure his land furrow by furrow with the ashes—an idea which I must not yet indulge, lest I should be thought fanciful beyond the due proportion.

But my mechanical impetus is not to be thus instantly checked. If what I hope, can be realized, there are properties in this invention, for locomotive engines, superior to any the steam engine itself can boast. A light Machine: a light combustible: no water to carry; no steam to condense, &c. &c. As however I have never tried this felicitous creation, I assert nothing.

But again, this seems to be a really good method of distributing heat in any useful direction: for there is an impulsive force which not only requires no draught to make the fire burn, but will drive heat to any distance through pipes of any form, and placed in any position. There is therefore, a certain utility attached to this Machine, whatever may be it’s merits as a power engine. Our present methods—of destroying coals—are excellent! but our methods of making them useful are defective in the extreme. If you have no draught in your chimneys you are stifled with smoke. If you have much draught, you have little heat—for the chimney swallows it, and half your room is in Norway. Use then an impulsive system, (of some kind) and you may send your caloric down into the cellar to be drawn from thence as wanted, for the upper apartments.

But my subject pullulates as I proceed. This idea is by no means exhausted. It is not an indispensable feature of it, to heat rooms with the same air that fed the fire. For instance, if a fire were made under the vertical cylinder K, and led into and through it by a proper pipe, almost filling it—then the cold air of the pump A B would pass round that pipe to the working cylinder C D, and there impel it’s piston E as before. Not perhaps so strongly; but with an air uncontaminated by burning, or by ashes—and therefore more congenial with some uses of the Machine. In fact, air thus introduced might be perfectly fit for breathing, and still get elasticity enough from this passage, to force heat to the bottom of any room we wished to have warmed; whereas, by using only the levity of heated air to give it motion, we scorch the tops of rooms and factories, and unmercifully freeze the bottoms. I must beg leave to be a little severe on this point:—since for a thinking people, as strangers call us, we have been extremely thoughtless in this respect: so that as much seems now to do by way of introducing comfort into our saloons, as was done about the year 1200, when those chimneys were introduced that are now become a kind of nuisance. In a word, and I am serious when I say it, the present arrangement of our chimneys, is in my humble opinion, essentially unphilosophical; and as such ought to be speedily discontinued or greatly modified.

In the above pages I have laid myself open to much animadversion, by a kind of cast for much honest fame. I have let the public into my secret—I have thought aloud: And if the greater part of these cogitations should prove to be imaginary, I shall only plead, that they are drawn from the same source as the many useful Machines I am known to have devoted to public utility.

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OF
A ROTATO-GYRATORY CHURN.

This title I confess, seems very ambitious, as applied to an utensil for the dairy: but I had to express the combination of it’s own axis, and those of the leaves or wings about their respective axes, while gyrating round the common centre.

The principal shaft A B, fig. 8 and 9 of Plate 24, is the general centre of rotation; and a b are two lighter shafts carried round that centre, and turning at the same time on their own centres by means of the wheels e f geering in the fixed wheel c d, (of which one half only is drawn) and which forms part of the top of the churn. Each of the shafts a b, carries four leaves or wings (better seen in fig. 9) reaching from the top, nearly to the bottom of the vessel; and they run in proper steps in the cross piece m, and also in proper collars in the upper cross piece g h. In fine their wheels e f, and the fixed wheel c d, which turns them, are furnished with teeth on my patent principle; and therefore work without noise or commotion. Now, the principal shaft A B, rests on the step B at the bottom of the vessel; and runs, at top, in a collar formed in the metallic bridge i k, which, fixed to the outside rim of the cover, passes directly over the centre of the Machine. When therefore, the cream is put into the churn, (to do which the above mechanism is taken out) the mechanism is re-placed as now represented; and the main shaft set in motion by any convenient power: when the side shafts a b, turned by the fixed wheel c d, give a backward motion to the wings a b, and create a great agitation of the cream—for, it should be remarked, that this is not a circular motion: but each fly produces a kind of vortex round it’s own centre, while progressing round the common centre. The consequence of which, as above intimated, is, an unceasing agitation of the liquid, and, I believe, the best of churning. This however, I state as a mechanician, not having been initiated into the secrets of the dairy properly so called.

It may finally be observed, that the leaves or partitions l n, fixed to the sides of the churn, (beyond the reach of the moveable wings a b) are destined to prevent still further any general motion of the butyraceous matter; and thus to accelerate the churning process: and further these leaves, both fixed and moveable may be pierced with holes, like the analogous parts of other utensils of this nature.

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OF
A HELICO-CENTRIFUGAL MACHINE,
For raising Water in great quantities.

The screw of Archimedes, is well known. When used to raise water it is placed obliquely, in such a position as that it’s hollow threads become more oblique to the horizon than the axis of the screw itself: observing which practice, some have said of this Machine, that it raises water by letting it run down: But this cannot be true. The threads of the screw merely wedge themselves under the water, and make it rise in a direction parallel to the axis of the screw; at the highest end of which it falls into the upper reservoir.

I once placed a screw of this kind upright, and said (in thought) is it then impossible to raise water by means of this screw thus placed? The answer in a few minutes was—“not at all; there is a force would make it easy: namely, the centrifugal force:” and this mental soliloquy was the origin of this Invention, which, some thirty years ago, I shewed to a public man, whom the lovers of the mechanical arts will long remember.

In Plate 25 fig. 1, A B are two screws, perfectly like those used in exhausting watery foundations; and named of Archimedes. They are placed perpendicularly in the frame C D, so as to turn in the cross bars a b, c d, fixed horizontally on the main shaft E F of the Machine. At the bottom of this shaft, E F, (which turns in a step on the sill G D) is a low cylindrical vessel, shewn by a section only at e f, which dips into the under water nearly to the brim. It is used to carry, in proper steps, the centres of the screws A B, and, being pierced with many holes, to feed them amply, without exposing their motion to any resistance from the stagnant water. These cylinders A B are merely indicated as screws by the threads, dotted between h and d and e and g, and their upper mouths are seen near a b, just under the cross piece marked with these letters. These screws then, are turned by the wheels i k, as actuated by the fixed wheel m n, in the same manner as those of the churn before described; which in fact, is a corollary from this Machine, but of much later date. To return to the Helico-centrifugal Machine—the screws A B are terminated above by circular plates o p (marked with the same letters in fig. 2 and 3) intended to receive the water from the mouths of the screw-threads a b, and carry it on to the plate q q, which insures it’s further progress into the ring canal r s, also shewn by a section only, to prevent confusion in the figure. Now what raises the water in these upright screws, is, it’s own centrifugal force, combined with the revolution of the screws: for while this central force is urging the water outward, the screws are bringing their sloping threads like wedges, against that tendency; and the consequence is, that the water actually rises perpendicularly till it flows over the ledges or rings o p, on the plate q q, and thence into the ring canal r s, from which it is conveyed to any place desired.

If this Machine is well made and proportioned, I think it is one of the best that can be used, to do much work by a given power: It gives no shock to the water; which, when once in motion, continues to rise, and escapes when arrived at it’s proper height: and, being spread over a large surface, no part of it is raised higher than enough. The perfection of the Machine depends on a due relation between the centrifugal force, and the sine of the angle, which the threads of the screw make with the horizon; and this may be modified by the diameter of the wheels i k, as compared with that of the screws A B.

The figures 2 and 3, are two views of the upper part of the Machine. They shew, and mark with the same letters, the cross bar a b, the inside of the screws, and the circular plates o p, together with the circular conducting plate of which q q, fig. 1, is the section. Fig. 3 shews the fixed wheel m n, the two screw-wheels i k, the cross piece a b, and under them the plates o p of the 1st. and 2d. figure.

One other object claims our attention: The threads of the screws (whether more or less numerous) should each be furnished with a valve at bottom: that the water may not run out when the Machine ceases working.

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OF
A FORGING MACHINE,
For Bar Iron, Steel, &c. square or figured.

This Machine acts by pressure instead of percussion. But this pressure is so instantaneous as to resemble a blow, and so often repeated as to produce a considerable effect in a short time. The means are represented in fig. 4 of Plate 25.

There, A is a mass of metal answering the purpose of an anvil, but having two surfaces, situated at or nearly at right angles to each other, on which the metal is alternately struck or compressed. The two sides of this mass A, are perforated by two holes, properly bushed, in which turn the crank shafts B, C: the latter furnished with the bevil wheels D, E, which geer into and receive motion from two equal bevil wheels F, G, fixed on the main shaft H I, and to which the power is applied. It is thus evident that the two crank shafts B, C, will make the same number of revolutions; and that if one of the rollers K, L, is placed on the excentric arm of one shaft, and the other roller on the other (their position being as in the figure) that then the rollers K L will impinge alternately on any bar, held in the angle M, and forge or extend it, and finally leave it reduced to the same dimensions, in it’s whole length, if, by hand or proper machinery, the bar has been drawn or pushed along the angle M, in a manner analogous to this motion at the tilt hammer. It is also clear, that the size of the bar will be determined on a given Machine, by the diameters of the rollers K L, compared with the distance of the shafts from the angle M of the anvil.

It may be of use to observe, that the effect of this Machine is not confined to square bars: since with unequal rollers K L, it will produce flat bars; and with rollers properly grooved, (the piece M being formed accordingly) it will produce round iron or steel of better texture (I presume) than when taken from the slitting-mill, and merely passed through grooved rollers. I expect, at all events, a rapid effect, from four or five hundred turns of the cranks per minute.

It will occur to every mechanical reader, that the mass M, which is tempered and adjusted to the principal anvil A, may be still more varied in form, so as to give other results besides those above anticipated. Nor need it be said, that the shafts B C might run in steps capable of being screwed up to their work, even during the process, should any such motion be expedient. These are details I do not wish to dwell on in these descriptions—where I endeavour to make known general and essential properties, leaving particular views and cases to my reflecting readers.

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OF
A RECIPROCATING HORSE WHEEL,
For Mines, Mangles, &c.

I believe there is no better floor for a working horse to tread on, than a plane of wood—on condition, of the horse being rough shod: I speak however, on recollection of many years’ standing. I then felt persuaded that a horse wastes less effort by travelling on this floor than on any other; which is one of my reasons for the adoption of the present Machine. It consists (Plate 26, fig. 1,) of a wheel A B, on which the horse walks, as indicated by the sketch of him given in the figure. Besides this, he is placed between two shafts C D, affixed to the lever E F, the latter carrying round with it, at intervals, the drum G, whose office it is to raise the weight I, whatever kind of resistance that weight represents. This lever runs by means of it’s cannon L, on a round part of the shaft common to it and to the drum G. Moreover, there is a second drum H, destined to raise the weight K, whatever kind of resistance that represents. Both the drums, G and H, turn on round parts of the main shaft M, but are alternately connected with it—first, the drum G, by the rising of the bolt a into it; and secondly, the drum H, by the falling of the cross piece b c, between the studs e d affixed to it. Now, this cross piece b c, is part of a T-formed bar, that penetrates the centre of the shaft as low as f, where it rests on a transverse lever f g, connected to the right with the bolt a above mentioned, and forming a branch of the bent lever f g h, which works the bolt h i under the wheel. In the present state of things, if the horse steps forward, he draws the shafts C D, round the common centre; for the wheel is immoveable by means of the bolt i, which takes against some fixed object at k: and thus will the weight I be raised. And when this motion is achieved, the handle o is raised a few inches, which brings it into contact with the obstacle p, and puts a stop to that motion of the lever E F. At the same time the bolt a, is drawn out of the drum G, and the cross piece b c is let down between the studs of the drum H, while, by the bent lever f g h, the bolt h i, which held the wheel, is drawn back, and then the horse, instead of progressing round the centre of the wheel, is himself brought locally, to a stand; and without even knowing it, (for he is blinded) he now treads round the wheel in a backward direction, and raises the weight K, while the drum G permits the weight I to descend by the uncoiling of the rope, till this operation has likewise produced the desired effect—when things are again placed in the state first observed. One thing remains to be noticed: It is, that both these motions might have been produced by acting from a fixed point on the central bar b c f, through the upper gudgeon of the shaft, instead of using the handle o, as before directed. It is even easy to conceive how the Machine may itself be made to perform these changes, and thus to produce the whole effect without any personal care or attendance.

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OF
AN EXPANDING VESSEL,
For Steam Engines, Pumps, Blowing Machines, &c.

It is one of the simplest and most perfect operations of the mechanic art, to form a flat surface: witness the process of grinding looking glasses, and forming one plane from another. Nor is it, necessarily, more difficult to place two surfaces parallel to each other, by means of three or more pillars with proper shoulders, or counternuts against which to screw the plates from behind. It is therefore easy to compose an expanding and contracting vessel, that shall become a mover by the force of any fluid, elastic or not, or shall act as a water or air pump, when driven by a convenient power; or both together, when this combination may be desirable. Thus, in Plate 26, fig. 2 and 3, A B C D is a box with four sides and four jointed angles—which, if one of it’s sides, D A, be fixed to a given position in the cage or frame E F G H, will expand or contract according as the sides A B and D C shall rise toward the perpendicular, or fall toward the horizontal position. The dotted lines A 2, A 4, A 6, &c. shew that the successive capacities included in the vessel, are respectively as the sines of the angles which those sides A B and D C make with the horizon; so that, although this device furnishes an unequable power, yet it is equable enough for many purposes in the first few divisions D 3, D 5, &c. and might be altogether equalized in it’s effect if necessary. Let us suppose then, that the aperture 8, brings steam into this vessel: The lid B C will rise to 6, 7, when, if the pipe 9, communicating with a condenser, be opened, the steam in the vessel will rush thither and be destroyed: when the atmosphere will press on the lid B C, and cause the vessel to collapse with a power proportionate to that area; for the sloping and parallel sides A B and C D counterpoise each other; where note, on occasion of the pressure which I am now speaking of, that the ribs or bars L M, are used to strengthen the sides of the vessel, and thus prevent it’s fracture under this pressure.

From this manner of making these expanding vessels, it follows among other things, that if the frame E F G H were surrounded with wood or any non-conducting substance, and made to communicate with a warm close room, the atmosphere thus acting on the vessel would not cool it, and that therefore, an atmospheric engine, would, in this respect, be as good as a steam-acting one. But steam might be introduced into this outer case, and act as a spring to reciprocate the internal effect of the same agent.

The third figure of Plate 26, offers an end view of this cage or frame, shewing the expanding vessel at B C A D, where the strengthening ribs of fig. 2 are seen endwise at 1, 3, 5, 7, &c. and moreover, F G and H are the pillars or cross bars by which the parallelism of the two end plates is effected and secured.

There remains an important subject to be considered: How to make the corner joints D C, and the end joints steam or water-tight as required. The small figure 4 answers the question as far as water is concerned. A is a strip of leather screwed more or less near to the edges of two contiguous sides of the vessel, so as to cover the joint or hinge, and make it water tight whether the pressure come from within or without. This figure also shews the grooves which receive the stuffing to close the ends of the vessel, by sliding against the plates or cheeks E F, &c. fig. 2. The several members of the corner joints themselves should be well fitted into each other: so indeed as almost to close the vessel without any stuffing. Nor need we in all cases be anxious about this stuffing; for I think it very possible to make this joint close enough for pumping or blowing without any such provision. I observe, however, that the leather A, fig. 4, might give place to a strip of thin metal, bent into the same form, (or nearly so) the elasticity of which would leave play enough for the joints, on the supposition of working only with a moderate degree of motion in the said joints.

I should not have given this idea so much attention, had I merely wished to use it where the cylinder-motion now applies: But my present views go further. I foresee the use of this Machine for very low pressures—and in very large dimensions; and I can conceive a proportion between it’s length and height, that shall as it were annul the effects of friction and leakage, compared with those of the cylinder-formed piston. But I do not undertake, or hardly wish now, to exhaust this subject: being more anxious to deliver the idea to my readers, than to announce all I intend to undertake by it’s means. I shall, therefore, merely finish the description of the other figures 5 and 6 of this Plate. The first, is a small hand pump on this principle, having a suction pipe A, and a rising pipe B, both having proper valves and opening into the expanding vessel, as worked by the handle C, much in the manner of a common pump. It will therefore act by it’s expansive and contractile properties; and have one good quality we should seek in vain elsewhere—It will begin the motion of the water with a softness unknown in the use of pumps in general.

In fine, the sixth figure shews a System of this kind applied to the two objects, of giving power, and using it. The vessel A B, receives the power from steam or any other agent; and the vessel C blows a fire, raises water, or does any analogous work, without requiring any other parts than those here displayed.

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OF
A GOVERNOR, OR REGULATOR,
For Wind-Mills, Water Mills, Steam Engines, &c.

This Instrument was first intended to regulate the grinding of a wind-mill; and was used for that purpose in Kent, some time before my departure for France, in 1792. It is founded on the doctrine of opposite qualities—and is a practical combat between equal and unequal motions. In wind-mills, the mechanism is exposed to all the variations of a capricious element: and the common way of preventing these convulsive motions from injuring the flour, was for a man to attend a lever connected with the bridge tree, (which carries the upper stone) and by it to bring the stones nearer together when the wind was strong—and nearer still, when it was violent: and, contrariwise, to lift again the upper stone when the wind assumed a milder movement. A process this, which nearly equalizes the degree of grinding, but not so nearly the quality of the meal—for this is found to be more heated by great, than by moderate velocities. At all events I thought a Machine like the present, would regulate this process, as well as a man; and it was found to do so—except, perhaps, in very extreme cases.

This Governor, is represented in fig. 1 of Plate 27—the ground work of which is the same as that of the third figure in Plate 3: for in reality the present Machine claims the precedence of the Dynamometer; and may therefore, well borrow a figure from it’s description. A is the power-axis, receiving motion from any proper shaft of the mill. It is turned backward by that shaft, and therefore tends to raise the ball B—an operation equivalent to bringing the mill-stones nearer together. At the same time, the axis of resistance C, carries round a pallet-wheel D E, and by the pallet D, sets the pendulum F G a vibrating, which therefore, by every stroke, lets down the ball B, and thus raises the upper mill-stone. A proper position of the latter depends on the similarity of the motion of the power-axis A, which winds up the ball B, and that of the axis C, which lets it down. While these are equal, the weight B remains stationary, and the work goes on well. But if a gust of wind increases the speed of the mover A, (the pendulum F G confining the axis C to it’s usual speed) the ball B is immediately raised and the stones brought closer—which is what the grinding process requires: And should that gust increase in violence and become a hurricane, the intermediate cylinder M, while producing that effect, carries also with it the cord H I, and thereby raises the bob G of the pendulum, and thus fits this movement to the increased speed of the mill: raising, sometimes, the bob to the very centre F of it’s vibration, where it’s oscillations become rapid enough to unwind all the excess of motion which the hurricane had occasioned; until, the wind subsiding, the pendulum acquires a medium length, and things go on moderately as before.

It may be observed, that the present form of this Machine is not quite so simple as it might have been made; nor is it so simple as it first was. The required motions being much shorter than those of a Dynamometer, the cylinder M, among other things, might be dispensed with; and one of the intermediate wheels be likewise suppressed. And if we advert to the retarding principle which resides in the pendulum, the well known conical pendulum might be substituted for the present one; since from it would arise a regular or equable resistance, opposed to an equable effort. Some however, might then consider the conical pendulum as an ordinary centrifugal governor; and, as a mere retarding principle, it may be thought too complex for the occasion: but I think on the contrary, that it’s use in this connection, would make this Machine one of the best of regulators, as well for steam engines as for water and wind-mills of every description: especially if fitted up with my Patent Geering.

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OF
A MACHINE
For Forging Nails.

There is a strong analogy between this Instrument for forging Nails, and the Machine heretofore given for forging Bar Iron, Steel, &c. The process of kneading the softened metal, by means of a pair of alternating cranks, is the very same: but the acting bars or stampers A, B, are an addition to the former method. Plate 27, at figs. 2 and 3, gives a representation of the present Machine; which forms the nail almost instantaneously, by many contacts of the stampers a b, (fig. 3) on one of which the figure of the nail is engraven—or rather filed across that stamper, for no hollow figure is required by this System.

The second stamper c d fig. 3, whose place is at A fig. 2, is quite plain on it’s face; being destined merely to keep the metal to it’s thickness—as the particular nail here intended, is a floor nail, requiring a head on two sides only. As to the figured stamper b a, fig. 3, it meets a similar form in the anvil, as at e: and it is by the pressure of these half matrices, that the head is formed and the bar separated from the nail. It may be noticed that the stampers a b, c d, are shewn in the figures, as perfectly straight on the face: but the kind of motion resulting from that of the cranks, would require a gentle curve here, which a first experiment will sufficiently indicate.

Some skill would doubtless be necessary in presenting the nail bar to this Machine; but to make this operation the easier, there should be a guage, moving toward the working point e, by a given quantity for each nail: say that this guage comes forward at each time a distance equal to half the length of a nail; and that the thickness of the nail bar is so proportioned as to contain in that length, enough of metal for the nail when finished.

It remains to be observed, that the stampers or bars A, B, fig. 2, are contained, in the direction of their width; by two plates like f, connected with the anvil e, and leaving near e, an opening large enough for the nail-bar to pass easily.

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OF
A MECHANICAL ASSISTANT
For the Tea Table.

I shall, perhaps, be laughed at by some unfeeling censor, for including the tea table in the field of my mechanical speculations. But, in so doing, I seriously mean to be not only attentive, but useful to the ladies—who, I am old enough to believe, deserve this service at my hands. My object is to obviate for them the necessity of tediously wielding a ponderous tea-pot, until real and painful fatigue ensues: thus emphatically making a toil of that pleasure they had hoped for in administering comfort to others.

This new method of tea-making admits the use of the common tea urn—which is placed on the table near the left hand of the fair distributor. This arrangement is given at figs. 4 and 5 of Plate 27. There, A is the Urn; and B any common tea-pot, for whose spout, the cock a, has been substituted; and the handle of which has been slightly modified, so as to make it a proper centre of rotation. This tea-pot is, of course, opened before it is brought into the position shewn in the figures. At C b c, is placed, first of all, on the table, a stand of metal, terminated upward by the stem C D which forms a vertical centre to the whole apparatus: and which is sufficiently fixed to the table by standing on three feet, b c, &c.; under which are stretched small pieces of Caoutchouc (or India rubber), which, by their adherence to the table, make the whole steady. By these means, the tea-pot can be turned round, by a gentle effort, till it comes under the cock of the urn, from which it receives the boiling water. And, finally, the tea-board, which is itself circular, revolves on the same axle C D, supported by the casters or rollers e f, and bringing successively all the tea-cups m, n, o, &c., to the spout of the tea-pot, where they are filled without the smallest difficulty, as will appear by a further inspection of the figures, and especially by an appeal to experience.

The above, I should presume, is all that need be said upon the subject. It remains for some rationally zealous friend of this social repast, to put these (or other analogous) ideas in practice: in which enterprize, should he succeed in pleasing the ladies, he may depend on the approbation of every lord who deserves the name.

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OF
A COPPER-PLATE PRESS,
With curious and useful Properties.

This Machine, as intimated in the Synopsis, was invented expressly for the use of the lithographic art, as an improvement on the roller press used in Paris when that process was first introduced there. I have, however, seen in England the description of a Machine which takes the desired impression without any rolling motion. This Machine, in that description, carries a kind of scraper, or, as the calico printers would say, a Doctor, which, pressing on a line only (while drawn over the paper, or the paper under it), acts successively on every part of the sheet, and, no doubt, gives a good impression. Of the relative perfection of these methods, I do not presume to judge, as it is a technical question; and both Systems are, or have been, used. But, when intense pressure, joined to much precision, and great economy of power, are desirable, this Invention appears to me superior to any thing I have seen used for these purposes.

In fig. 1 and 2, (see Plate 28), A B are two horizontal planes of hard wood or metal, connected, at a proper distance, by the pillars C D, shewn in fig. 1 only. E F are two Sectors of a large cylinder, united at the point a, either by a good hinge or by a joint composed of a hollow prism fixed to the upper sector E, and of a solid one, more acute, fixed to the lower sector F; so that, in the latter case, this joint works with an insensible degree of friction, and thus occasions a great saving of power.

In the working of this Press, the joint just mentioned, however made, describes a straight line, parallel both to the floor B G and the ceiling H A, which have been already shewn to be parallel to each other: and thus are the joint a and the sectors E F suspended to the cap or ceiling A H by a pair of triangular braces I a K, which slide smoothly in two dove-tailed grooves A m. Moreover, to the lower sector F are fixed two working arcs b c, one on each side of the Press, and whose radii are exactly equal to that of the upper sector E (whose circumference, therefore, is invisible in fig. 1.) Further, just above these arcs, and in the middle of the slide I K, are placed, on proper centres, a pair of grooved pulleys P, destined to work the under sector, without disturbing the motion of the upper one, which latter is a rolling motion under the aforesaid ceiling A H. For the said purpose, a metallic cord or chain is fixed at m (fig. 1), which, passing round one of the pulleys P, is led to the end n of the arc b c, n o; and near A is fixed a similar cord, which, carried round the other pulley at P, is led to the angle o of the same arc b c, n o. By these means, the sector F is fixed both in place and position, as long as the slide I K retains it’s present position and state. But, again, a system of similar cords, placed under the ceiling A H, near the edges of the upper sector E, determines the place of that sector, in every case, except a change of position; for a rolling motion can still have place, without occasioning any other change.

When, therefore, a pulling bar, a crank and fly, or any other prime mover, applied at the joint a, carries that joint (say) toward the pillar D, that motion takes place without any rubbing of surface either above or below; for, when the upper section has rolled under the ceiling A H, into the position n p q, the lower section has rolled upon the plate s t, into the position q r s: in such sort that the analogous angles o t, p r of both sectors are always found in the same perpendicular line—or plane—o t, p r; the cause of which I shall now endeavour to unfold.

When a wheel, in general, rolls on or against any fixed plane (and the cords m P, A P, now act the part of a fixed plane), the point of it’s circumference the most distant from that plane, moves, in a direction parallel to it, just twice as fast as the centre of such wheel, because it is twice as far from that plane, the virtual centre of its motion: (an example of which is found in the wheel of a carriage, whose top moves forward just twice as fast as it’s axle-tree.) Supposing, then, in the present case, the frame I a K, with the pulleys P to glide toward the right hand, the cord A o fixed near A, will turn the arc b c to the right, twice as fast as the centre of the pulley P moves in that direction: and if this impulse had acted on the joint a, while fixed in position, the arc b c would have turned too much by half. But it so happens (if this expression may be used), that the joint a itself moves in that direction once as fast as the pulley-pin; so, that the motion remaining to the sector F is a single motion, merely sufficient to keep the two sectors E and F directly under each other, or within the same perpendicular lines p r, n q s, &c.

Thus, it appears, that the turning motion of the two sectors is the same; and that a given point of the lower one will always visit the same point of the corresponding plane s t, independently of contact with any substance lying on it; and that, therefore, the pressure, though successive, is perpendicular, having no tendency to displace or pucker the paper laid on it; besides which, it may be observed, that the power of this Press is immense, from the length of the radii of the sectors E F, and the absence of any rubbing motion.

I observe, further, that racks, made with teeth on my principle, either singly inclined with cheeks, as in Plate 14, or with teeth in the V form, will produce a more certain effect than the cords and pulleys above described, provided the arcs b c, and the upper sector E, be prepared and toothed accordingly.

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OF
A REFLECTOR
For Lighthouses, &c.

The object of this Invention is to join economy of light with splendour of effect. The means are the following:—

From the nature of reflecting curves, it follows that the smaller a luminous point is, the more perfectly will its emanations be reflected; for a focus is a point of the smallest magnitude, if, indeed, it has any dimensions. My idea, then, is to make a focus of a line of light very minute in it’s section, but as large, in it’s contents, as may be desired: thus securing a considerable fasces of luminous particles while using them in an economical manner. To this end (see Plate 28, figs. 3 and 4), I form my reflecting surface of two distinct parts, having a section common to both, viz.—1st. a concave-parabolic-spindle, represented at A B C, as cut by a vertical plane passing through it’s centre; and 2ndly, a parabolical bason E D F G (represented in the same manner) surrounding the former, and so placed as that these surfaces have a common focus—namely, the circular line of which a b is the section; the line itself being shewn by an elevation passing behind the aforesaid spindle A B C. This linear focus, therefore, may be two or three feet in diameter; thus imitating the tenuity of a punctual focus, while emitting a large quantity of rays.

This Lamp, then, consists of an oil vessel, which is formed by the outside of the parabolical bowl before-mentioned, surrounded, in it’s turn, by the cylindrical surface P H, I Q, this vessel communicating with the wick-ring a N, b O, by a passage, H I, made as thin as possible, in order to leave the light at greater liberty to pass downward after reflection. (Where it is proper to add that the wick-ring is drawn too thick in the figure.) Now, it is well known that all rays of light issuing from a point, and falling on the concave surface of paraboloid belonging to that point as a focus, are reflected from it in lines parallel to each other; and, therefore, a great part of the particles emanating from the linear (or circular) focus a b, and impinging on the surfaces F G A B, and B C D E, will be reflected perpendicularly downward, as at a, 1 3; b, 2 4, &c. and this being the case all round the common centre B, there will be formed a cylinder of light of the diameter H I, diminished only by the shadows of the wick-ring, the passage H N O I, and the pillar B L, when that is used, which is not indispensable.

If this cylinder of light strikes on the plane mirror K H, placed at an angle of 45° from their direction, these rays will be reflected horizontally, and, preserving their cylindrical form, may serve as a powerful beacon to the benighted mariner; the more useful, because susceptible of those temporary variations of direction and aspect, long since employed to distinguish one station from another.

But, if it were desired to illuminate a large space at sea, or elsewhere, the aforesaid cylinder of rays would be received on a conical surface K L M, which would give it the form of an immense sheet of light, of a thickness (allowing for aberration) equal to the height of P L M, of the same conical surface.

I shall add only one idea—namely, that to light any round space, building, theatre, &c., this system might be made very efficient by throwing the sheet of light M P higher or lower on the walls, &c.; or (altering the angle of the cone K L M) by bringing it down to any position in or below the horizon, as circumstances may direct.

It would be superfluous to say that this Lamp might be furnished with all the advantages of the argand principle; or, the whole wick-apparatus might be superseded by a circle of minute, and very numerous gas lights, forming, sensibly, the same linear focus; or a thin circular slit might produce a real ring of light, strengthened by all the resources of this new and splendid discovery.

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OF
A LONG PARALLEL MOTION,
For Mangles, and other Reciprocating Machines.

In the year 1793 or 4, I received a written problem, desiring me to give a plan of a long Reciprocating Motion, that should be driven by the pit-wheel of a common water-wheel, of given dimensions, and placed in a given position. In a few days, I produced the drawing now represented in Plate 29. Its object, as required, was to move the cylinders L M, figs. 1, 2, 3, backwards and forwards, in the long grooves or gutters N O, for the purpose of crushing or bruising their contents: but what those contents were I never knew. I, however, produced this Machine, considering it as a general thing, and of a nature to perform most operations of a similar kind. The Machine consists—first, of a long rack I K, much like a narrow ladder placed on it’s edge, and in the teeth of which work those of a pinion p, whose axis q is connected with the wheel r, which receives it’s motion from the vertical wheel s t, which is the pit-wheel in question. This communication takes place by means of an universal joint x, being a mean of permitting the pinion p to vibrate from side to side of the rack I K, when arrived at either end of it. For example, the pinion p now turns from left to right, and, being on the other side of the rack, and held by the chain v, it drives the slide P Q in the same right-handed direction, and, with the slide, the two heavy cylinders L M before-mentioned;—for, the said slide P Q carries across it’s middle the axle-tree S T, which is the centre of both these cylinders, and connects their motion with that of the slide now in question. Further, there are rollers placed between the cheeks V V, on which the slide moves horizontally, as guided by other rollers, placed at the points 1, 2, 3, 4, &c. Again, the ends of the axle-tree S T are furnished with two bow-like bridles, which, connected with the pulling bars Y, are again fastened to the slide P Q, at the two ends of the present figure.

When, now, the pinion p turns (see fig. 1 and 3), the rack, slide, and cylinders roll in the grooves, till the end of the rack comes to that pinion; which, finding no more teeth, swings round the last, and taking a new position, reverts the motion, till the other end of the rack comes to it, and occasions another return: ad inf. This will be better seen at the third figure, which is an end elevation of a part of the Machine.—There, P shews the slide and one of the teeth of the rack (which teeth are longer than the rest, as seen near L M, in fig. 1.) In this figure, we see at A, a mass of brick-work, covered by the sleepers 5, 6, 7, &c., on which the long cheeks V V repose. There, also, the chains v z are seen, connected with ring-bolts, which go through the bars a b, and are nutted on the other side of the spring-beams c d, in order to avoid the commotion which would otherwise attend every change of motion in the slide and cylinders. For this purpose, also, and especially to prevent any waste of power at these moments, there are mixti-linear wedges laid in the gutters, such as are shewn at 6, which are formed so as to absorb the momentum of the cylinders, in exact conformity to the time employed by the pinion p, in swinging round the end tooth of the rack; and thus to save all the power and time possible.

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OF
A MECHANICAL SYPHON:
Which expels Part of it’s Water at the upper Level.

An ordinary Syphon acts by the pressure of the air on the upper water, which drives it into the ascending pipe, because there is a (partial) vacuum made there by the weight of the falling water in the descending pipe; this being always longer than the first. Thus, in Plate 29, fig. 5, A B shews the rising pipe of a Syphon, and C D the falling pipe, which is longer, and sinks to a lower level D, than that A of the water, which feeds the machine. E, in this figure, represents the vessel containing the mechanism on which the new effect depends: and which I shall now describe.

B and C, fig. 4, are, one the ascending pipe A B of fig. 5, and the other the descending pipe C D. They are surmounted by two cylinders, of unequal capacities—this inequality bearing a given proportion to the difference in the heights of the rising and falling branches of the Syphon. In each of the cylinders works a piston a, b, which, I think, need not be stuffed, but well fitted. The large piston has proper valves in it, to let the water pass upwards, at all times; and the small piston has a valve i, opening upwards, by means of the mechanism we are now describing; and closing itself merely by the arrival of the piston into it’s present position; for the screw c prevents the valve from rising higher: e, f, are two arcs belonging to the lever E, and being circles round it’s centre of motion. They are cut into teeth, on my Patent principle, and work in the racks similarly toothed, which give motion to the pistons a b, or receive it from them. Further, behind the stand F, common to both levers, vibrates, on a pin, another lever g h, the use of which is to work the aforesaid valve i in the small piston; and this it does, by means of the weight h, in the following manner:—The machine being supposed in the present state, the Syphon will act, as usual, through the valves of the large piston; and the water pressing on the small one, with a power proportionate to the excess of it’s column over that of the other piston (a), will raise the latter as fast as the piston b descends; but the area of the piston a being larger than that of the piston b, there will be a pressure within the vessel b c d a, that must expel (through any prepared aperture at the top) a quantity of water equal to the difference of area between the two pistons, multiplied by the stroke of both: the real quantity of which will ultimately depend on the difference of level between the higher and lower water; or between the lengths of the rising and falling branches of the Syphon, B and C. When, therefore, this stroke is made, the end h of the lever g h, which carries the ball, will touch the screw d, and stop the descent of the valve i, which will thus be opened; when the water will have free egress through the descending pipe C, and the piston b will then rise through that water by the weight of the piston a, the valve i being kept open by the action of the weight h, until the piston b has risen to it’s present position, when a new stroke is prepared, for the same reason as before: and thus may water be carried over a hill of (about) 30 feet above the level of any stream or pond, and dropped into a lower canal on the other side, with the condition of leaving a part of that water upon the hill, proportionate to the difference between the level from which the water is brought, and that to which it is carried.

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OF
A FORCING MACHINE,
For taking on and off the Cylinders of Calico Printers.

The two figures, 1 and 2, of Plate 30, are intended to make this Machine known, assisted by the following description:—The first is a front view of it, and the other a partial view from above. In the former, A B is the frame formed of, and firmly connected with the two columns C D, which are fixed strongly to the ground, at such a distance below the ends C D, as to place the aforesaid frame at the height of about two feet, or higher, if convenient.

In the two cheeks of the frame A B, are cast or bored two round holes for receiving the gudgeons of the swivel E, one of which gudgeons is also seen at E, in fig. 2. This swivel turns in these holes; and it is itself perforated with a round hole just large enough to receive freely the body of the mandrel F G. This mandrel has now on it the cylinder, which is to be taken off. I K are, moreover, two ears or studs cast or welded on to the top and bottom of the said frame A B, and at exactly the same distance from the centres of the swivel E before-mentioned. These ears receive the ring-formed ends of the bars L M; see also the bar L, in fig. 2. To these bars is firmly fixed the cross-bar N O, which forms the nut of the screw P, by means of which the operation of the machine is duly prepared; for, now the cup Q (in the centre of which the screw P revolves against a proper shoulder) receives the end G of the mandrel, which it presses forcibly, while the whole is in the position E L, of fig. 2; that is, when the two centres E and R form one right line with the bar L, figs. 1 and 2. To complete, then, the process of driving out the mandrel, the bars, mandrel and cylinder are, at once, strongly made to describe the arcs a M b, a c; the mandrel revolving round the centre E, which is that of the swivel and the bars round the stud R. But, in thus revolving, a given point of the mandrel describes the quadrant a M B, and a contiguous point of the bars L M describes the quadrant a c; insomuch, that the mandrel must have been forced out of the cylinder in direction G F by the distance c b; where we observe that, at the beginning of this motion, the two curves a b and a c coincide in their movements, and only begin greatly to diverge from each other in the latter parts of these motions (see M b c.) The power, then, of this machine, when the cylinder sticks fastest to the mandrel, is infinite: and this power becomes weaker, and the velocity greater toward the end of the operation; that is, when the cylinder has slackened on the mandrel, and no longer requires to be driven with the same force as at the beginning. It may finally be observed, that the bars L M are suspended by an oblique bar or chain S N to the ceiling of the room just over the stud R or I, which is their real centre of motion, in the above-described process.

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OF
A SYSTEM OF MACHINERY,
For cutting and trying Tallow by Power.

The wheel A B, Plate 30, fig. 3, was a horse-wheel, but may be a first motion of any given kind. It is placed on the ground-floor; and over it’s centre is another shaft, having on it’s upper end a chopping block C, which revolves with the wheel A B, as turned from below. In this wheel, A B geers a pinion D, driving the lateral shaft D E, which has two functions: the first to work the lying shaft F, and by means of the cams G H, to lift the contiguous stampers; and, by means of the knives I K, to cut the tallow on the revolving block before-mentioned. Over this block is fixed an oblique scraper, which takes the tallow as soon as it is cut, and pushes it down an inclined channel, placed at C x, into the boiler. The second use of the shaft E is to turn the mill M, (better shewn at fig. 4), which is let down into the boiler, in one stage of the process, and drawn out by the tackle N, when not wanted. The use of this mill is to tear the fleshy parts of the substance, while in the act of boiling, and thus to disengage the tallow with so much the less heat, in order that it may be so much the less coloured. Besides this machine, there is a grapple L to be first used, which stirs the tallow in the boiler by the rotatory motion of the arm x. This position of the grapple would alone indicate what I have yet to observe—namely, that the boiler is a kind of ring, the section of which is the line 1, 2, 3, 4, and it’s depth 1, 2, or 3, 4. To prevent, still further, the fat from being burnt or coloured, the flue for the fire is conducted solely under the bottom of the boiler, as shewn by the dotted lines in fig. 5: the smoke or heated air being forced to make two revolutions under it, as indicated by the arrows in this figure, where we see more particularly the fire-place F in close connection with the rising shaft of the chimney at G; and this is so, because, with so great a length of horizontal flue, the fire would not enter the chimney till it had been heated to a first degree. There is, therefore, an opening into the chimney at a, and the fire, in lighting, is suffered to escape directly from the fire-place into the chimney; by which means, continued a few minutes, there is draught enough created to make the fire take its useful course through the flue afore-mentioned. I may just observe, reverting to fig. 3, that O shews the fire-place in elevation, and p the entrance into the flue, which last is double under the boiler, as shewn in fig. 5. Finally, the 4th fig. shews an end view of the tearing-mill, before-mentioned; but here on a larger scale, A B being a part of the side of the boiler.

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OF
A WASHING MACHINE, FOR HOSPITALS,
Which confines the offensive Matter till cleansed away.

Doubtless, the salubrity of every place, where many people are collected, would be much increased, if all impure exhalations were expelled as soon as formed; and this is especially true of those awful but sublime receptacles, provided by Philanthropy, for the sick, the wounded, and the dying! To assist in the work of purifying the atmosphere of these doleful abodes, was the object (30 years ago) of the Ventilator, presented in page 170 of this work. But, I conceive, that a share of evil, quite as great, resides in the putrescent qualities contained in or connected with the clothes, the bed-linen, the dressings, &c., of the inmates of an hospital; to whose sacred claims on the efforts of every good citizen, the present article is devoted.

This Washing Machine (see Plate 31, figs. 1 and 2) is a triangular (or square) box A B, furnished with a lid a b, so fitted, as, when screwed down, to be hermetically closed.—And, N. B., to facilitate this operation, I use in it a particular kind of screw (invented for the hose of fire-engines), which I shall now describe. I take a common screw, with it’s nut, and cut away the threads of both, at two opposite quarters of their respective circumferences, so that the screw can enter the nut to the bottom without turning; and the stuffing between the shoulders is so well fitted, in thickness, as to secure the penetration of the threads of the nut and screw the moment the latter begins to turn. There is thus a full quarter of a turn, in which the nut and screw will press as strongly as though the threads had not been cut away; and thus are nine tenths of the time required to use a common screw saved by this simple process: and thus, then, I close the lid afore-mentioned.

This Machine is further composed of a wheel C D, and a pinion E, to turn it with, either by hand, or by any proper application of power. The wheel turns the box A B, and thus agitates the contents in a way not dissimilar to the operation of the dash-wheels of calico printers. But, again, this wheel and vessel turn upon two hollow gudgeons c d; one of which is destined to convey cold water into the wheel from the reservoir F G, to regulate which is the use of the cock f: the stuffing box e being made as good as possible, in order to prevent all leakage, either of air or water. The second hollow axis d serves two purposes: it gives a passage to the fetid matter of which the expulsion is desired, and conveys it through the cock g to the sink or sough below h, without any communication with the surrounding atmosphere.

But we said this hollow gudgeon had a second use: it is to bring steam into the revolving vessel A B, from any proper boiler beyond K, when that part of the process requires it.—There are, moreover, two partitions C D, l m, made near the ends of the vessel, and pierced with many holes, in order to suffer the cold water to flow in, and the dirty water to escape, without choking up the respective passages: and, finally, at the eduction end of the Machine (see n, o, p, fig. 2), there are placed three pipes, reaching from the angles of the box to the hollow centre, and furnished, at those angles, with valves, opening outwards; which thus form a kind of hydraulic machine to raise this matter from those places to the hollow centre, and thus, after a certain number of revolutions, to expel it entirely.

The process, then, for cleansing the objects contained in the vessel A B (including the condition of cutting off all communication with the ambient space,) is as follows:—

1st.—These objects are dropped into the vessel as soon as produced, and the vessel is filled, one half or more, with cold water from the reservoir F G. The things are then left to steep in this bath for a day or two, or what space of time the periodical mutations of the house permit. By which operation alone, the miasmata are already much confined by the water, even though the lid of the vessel should be but partially shut: after which, this steeping operation may be continued, with the accompaniment of a few turns of the handle (E) to fully saturate every part of the mass. In the second place, a small stream of water is let through the cock f, and the wheel C D is kept turning for a few hours, to discharge the cold water and the most offensive matter, through the cock g, into the sink: and, thirdly, the steam-cock K is opened (that g being shut), by which means steam is brought into the vessel A B, and the whole soon raised to the boiling temperature. This state of things is continued, as long as it is found necessary; the motion, of course, being also continued, and even accelerated, that the mass of objects may fall from angle to angle, and be thus well washed—that is, well finished, if plain things; and fully prepared for finishing, by hand, if of a nature to require close attention. And, finally, in many cases, the warm process may now be abandoned, and a new stream of cold water be injected, accompanied by a due motion in the vessel, so as to rince the contents; and thus leave nothing to do for the laundresses, but to dry and mangle, or iron them; where, it is plain, that no inconvenience can have arisen from this process, either to these persons, or to the other inmates of the house.—Hence, then, this Machine has the properties announced—of confining the offensive matter until cleansed away.

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OF
A MACHINE,
For propelling Boats, on narrow Canals, without disturbing the Water.

The application of steam-power, to the motion of boats on narrow canals, is, I believe, much impeded by the consideration that the agitation of the water injures their banks, and would finally destroy them. On the other hand, it is known, that to drive a vessel, by acting on a fleeting medium, such as water, we must, at once, submit to lose about one half of the whole power employed—that is, the power, armed with energy enough to produce the required velocity, must go through twice the space that constitutes the way or progress of the vessel. This depends, however, on the size of the floats or paddles employed, compared with the section of the boat, as modified by the form of the prow; but it is difficult to employ a paddle so large as to suffer more resistance from the water than the boat itself; and, if they are found just equal, the loss of power is exactly one half of the whole. These, then, are the two difficulties which I hoped to avoid, by the method now to be exhibited.

The idea is this—To have a large and heavy wheel A connected with a long shaft B, reaching from the boat to the shore, and, turning that wheel in the boat, to propel the latter, by means of it’s rolling motion, on the bank or track-way; or, in some cases, on a proper rack, placed there for that purpose.

The Machine itself is represented in figs. 3 and 4, of Plate 31; fig. 3 being a stern-view, and fig. 4 a side-view, both of the machine and the vessel. C is an axis, placed along the vessel, and turned by any convenient power—as a horse, a steam-engine, &c. On this axis, considered as the first motion, are fixed the two bevil wheels b c, from which the long shaft B A of the rolling wheel takes it’s motion. The use of the two wheels b c, is to drive the boat in the same direction on whichever side of the boat the wheel A may be placed; for this, of course, must follow the track-way, which is sometimes to the right and sometimes to the left of the vessel.—Between the two wheels c b, is a sliding block (or catch-box) d, in which the shaft A B of the large wheel has it’s lower pivot, and by which it’s wheel B is almost instantaneously shifted from one to the other of the vertical wheels b c: the catch-box d being itself worked by a lever, of which the end only is seen at e, fig. 4. In fig. 3, there is further shewn a rope or stay f, which, fastened to the socket s, of the rolling wheel A, and fixed in the middle of the boat, at the greatest possible distance from it, serves to keep that shaft at or near an angle of 90 degrees with the boat’s side: so that (the vessel being long) it becomes easy by means of the rudder, assisted, perhaps, by lee-boards to keep the way of the boat in a line parallel to the shore, notwithstanding the tendency to veer outward, given by the wheel A, while acting on a point so far from the body of the vessel.

I further observe, that, in order to shift the apparatus, with a certain facility, from one side of the boat to the other, there is a mast M placed ahead of the mechanism just described, which rises as high as the length of the main-shaft (but can be lowered to pass a bridge, &c.), and to the top of which is fixed the block g, through which a rope passes from the foot of the mast to the above-mentioned socket of the wheel A. By this rope the wheel is hauled up till nearly ready to fall over the centre; when a push from below will complete that passage; and the wheel A, being afterwards lowered by the rope h i, will soon find it’s proper position on the other side of the boat, as before anticipated. Where, it should also be remembered, that this shaft must have a joint and socket, to permit it’s being bent, to pass a bridge, &c.

Hitherto we have supposed this rolling wheel to act on the bank or track-way solely by it’s weight; but this is not our only resource; for this wheel might be made of a moderate weight, and be pressed down by a brace reaching along the boat, toward the head and stern (see k l, fig. 3.), and hauled taught through an eye of the socket s; by which manoeuvre (the points k l being lower than the centre A of the wheel) the latter will be pressed forcibly downward, and cause that cohesion there, from which the boat is ultimately to take her motion.

And, as to the wheel A itself, I have not represented it in the very form I should wish it to have, because it can be sufficiently described in words. I should cast this wheel (if made at all in metal) as a shell, the outside of which would be what is really seen in the figure (at A), and the rim would have in it mortices, like those which are made for iron wheels destined to receive wooden cogs, and geer with cogs of iron. In fact, this would become a wooden-toothed-wheel, with its teeth roughly formed and placed, so as to occasion a small expence, and to be easily changed, when worn away by the friction on the track-way. Thus would, I am persuaded, a very moderate weight in the wheel, and as moderate a pressure from the braces k l, connect the wheel with the road enough to produce the desired effect, with a trifling loss of the power employed. And thus might we navigate a narrow canal, with a great saving of expence; not to mention that other advantage of avoiding entirely that injury to the banks, which must attend every system of propelling the boats, founded on the agitation of it’s waters.

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OF
A MACHINE,
For working, swiftly, the Slide-valves of Steam-engines.

The Slide-valve is an excellent substitute for the hand-geering of steam-engines, from the simplicity of form which it introduces, and the certainty of it’s recurring effects. But it is, I believe deservedly, reproached with being too sluggish in it’s operation, at the very moment when activity would be most desirable—namely, at the beginning of the strokes; insomuch, say some, that the power of the engine is materially lessened by it. The fact is, that the excentric (usually placed on the crank-shaft) is almost always moving, and with it the slide-valves also; which thus open by slow degrees, when they should open by rapid ones.

Without discussing the question further, I cannot refrain from introducing this application of the principle of my Parallel Motion, given in page 237; which appears to me greatly calculated to obviate these difficulties; and thus to leave the slide-valve in possession of all it’s own advantages, with the addition of those which have hitherto belonged exclusively to the Hand-geering System.

I have represented this Mechanism in figs. 5 and 6, Plate 31: where A B shew the crank-shaft of a steam-engine, working by means of slide-valves, the place of the excentric being at a b, in a line with the pulling-bar e f. Instead, then, of the usual connecting frame between the excentric at a b, and the valve-lever at g, I use for the above purpose, a lever e f terminated by an arc o, furnished (in the present instance) with five teeth, and connected by the joint e with the valve-lever g, in the usual manner. In the arc, which terminates this lever to the right, are the five teeth above-mentioned; and, they geer in the ten teeth of the wheel c d, which will be seen (in fig. 6) to be on the same shaft with the spur-wheel m, itself driven by the spur-wheel n, of twice the diameter. This wheel c d, therefore, makes two revolutions for one of the crank-shaft: and, supposing it to turn in the direction of the arrow, it will first of all draw upward the arc o, producing no effect on the valve-lever at g; but, when the tooth r is arrived at p (the tooth p being then arrived at the entrance of the curve q), the wheel c d will begin to draw the arc o along with it, round it’s own centre; and, the teeth of the arc being kept in it’s teeth by the similar curve q, the valve-bar will be drawn from g to h, in the course of one quarter of a revolution of the crank-shaft A B. But, now, the tooth r of the arc o will be found at s: and, therefore, the further revolution of the wheel c d will carry the arc o downward toward t, until the tooth r has reached the point t; that is, until the wheel c d has made another half-revolution, and the shaft A B another quarter; when, as before, the arc o, conducted by the curve t r, will again drive back the lever e f, till it comes into it’s present position: after which, their motions will be regularly continued. It is, then, evident, that the slide-valves are thus opened and shut, each during one quarter of a turn of the crank-shaft A B; and thus they remain stationary during another quarter, and that, in two positions of said shaft diametrically opposite to each other. And thus have we a simple mean, adaptable to every engine, of giving it much of the advantage of the hand-geering system, while preserving all that of the slide-valve principle. And, were it desired to lengthen the interregnum of the opening motion, it would be done by making the wheel c d smaller, and the ratio of n to m (see fig. 6) larger in the same proportion.

I observe here, however, that care should be taken not to make the valve motions too rapid, nor the intervals between them too long; for, I consider one of the best properties of this motion to be, that it acts like an excentric; that is, slowly at first, most rapidly afterwards, and finishes as slowly as it began; which is a precious quality in all reciprocating machines.

Finally, I would remark, that the two last rounds in the rack of the arc o might be rather larger than the intermediate ones, and turn, moreover, on pins, so as to suffer less friction when rolling on the conducting curves q and t. There might also be a plate or cap rivetted or screwed over all the teeth, so as to strengthen each one, by the force of the whole, as is shewn in fig. 1, Plate 29; from which, as before observed, this Mechanism is deduced.

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The foregoing completes the Third Section of my work: and gives an article beyond the twenty, first intended:—which I thought important enough to claim this distinction. I now beg leave to add a remark or two on the text and plates of this, and the Second Part, by way of clearing up some obscurities, that might otherwise embarrass my readers.

And, first, in fig. 1, of Plate 21, the receiving vessel M, erroneously appears to form part of the wheel D E; but is, in reality, placed before it, as in all similar cases.—And, further, a small deviation of the circular lines, in Plate 22, has set the plate and it’s description, in page 192, at variance; the difference between the lines o p and C q being not “imperceptible,” as there stated. I wish, then, that the dotted radius A o p, in the said fig. 2, may be carried (or supposed) halfway between p and C. Finally, in page 200, line 8, the 24th Plate is incorrectly called the 25th.

I shall conclude this Part, by an observation or two on the reception my System of Toothed Wheels, as described in this work, has met with—not intending to speak of the local difficulties I experienced at a former period. But, here, the interests of truth force me to break silence. The necessity I stood under of bringing out this work in Parts, has, at least, had one advantage: it has given me an opportunity of watching the workings of prejudice—not to say of envy,—and thus of neutralizing, in some degree, the effects of either: from which, however, I claim nothing but the right of making my labours the more extensively useful, by making them better known. I have, then, to say that, among a few other objections to the System, this error has come from so respectable a quarter, that it would be unjust to Science, and injurious to truth, to let it pass unrefuted. It has been said, that “my wheels are a Chinese Invention;” and this proof has been adduced of it—namely, a sugar-mill, from China, having it’s cylinders fluted in a spiral direction. Now, the fact is, it would have been difficult to give a better proof that the wheels are NOT a “Chinese Invention;” for two inventions are then only alike when they produce the same effect, by similar means. But here the effects intended are totally different. A sugar-mill acts in or near the plane of the centres; and one of it’s cylinders is not intended to drive the other independently of pressure between them. This is so true, that the rollers of many sugar-mills are not fluted at all. Besides this, my wheels exert no pressure in that direction; and if they did, they would not be cog-wheels. In a word, their action is at right angles to the former, and has an object of quite a distinct nature. These, then, are by no means the same machine; and, therefore, mine is not a “Chinese Invention.”

Here, however, I beg not to be misunderstood! I should feel no regret at appearing on the mechanical stage, a few hundred years after so ancient and astonishing a nation as the Chinese! But, in this case, truth did not permit me to sanction, by my silence, this flagrant error.

Finally, an opinion exists, somewhere, that these wheels will never be generally used, from the difficulty of making them; and this opinion has been expressed, apparently, with no very amiable feeling. But, amiable or hateful, the opinion is highly erroneous! It is so far from fact, that, in a competent manufactory, they can be made more cheaply than others now are; and many persons are already calling for them from every quarter; nor is any thing wanted to insure their immediate prevalence but a common degree of commercial energy.

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