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ILLUSIONS OF TOUCH.

APPLY the points of a pair of compasses, distant from each other one or two lines, to the cheek, just before the ear; then move them successively to several other parts of the cheek, and you will find, on approaching the mouth, that the points will appear to recede from each other; this effect being produced by the great difference of the sense of touch in these parts, It is a general law, that in the more sensitive portions of the skin, any two points appear to be further asunder from each other, than points of equal distance appear to be to a less sensitive portion. The same experiments may be made by holding together the extremities of the fore-finger and thumb, and then passing the tips of both in a line from the ear to either the upper or the under lip; as they approach the latter, they will feel to the cheek as if they were becoming more and more distant from each other.

If the skin be touched with the points of a pair of compasses, one inch asunder, the person so touched, while he shuts his eyes, will instantly be aware that his skin is touched in two places; but by continually drawing the two points closer, a degree of nearness may be reached at which the person will imagine his skin to be touched by only one body: he will, however, describe this body, or the compasses, to be a little longer in one direction than another; and it appears that this difference of length corresponds with the distance between the two points of the compasses. When these points are brought still nearer together, the inequality will no longer be felt, and the person will fancy he is being touched by one body only.

Handle a pea: it is one—place it between the first and second fingers of the right hand, in their natural position, and you will still feel the pea but as one. Then cross the two fingers, bringing the second over the first, and place the pea in the fork between them, so as to feel the left side of the pea with the right side of the second finger, and the right with the left of the first The impression will then be that you have two peas touching the fingers, especially if the eyes be shut, and the fingers be placed by another person. The illusion will be equally strong if the two fore-fingers of both hands be crossed, and the pea placed between them.

ILLUSION OF THE TASTE.

If the nose be held tightly while you are eating cinnamon you will perceive scarcely any difference between its flavour and that of a deal shaving.

THE GENERAL BLEACHER.

Provide some strong chloride of lime, soak in it strips of printed cotton; take them out, dry them, and you will find them very white, but very rotten, slitting and dropping into holes upon the slightest touch.

The dazzling whiteness of paper is caused by bleaching it with chloride of lime. Thus, if you write on printing paper with common ink, it will fade, because the chloride will destroy the colouring matter of writing ink. It will not, however, change printing ink, as that owes its blackness to charcoal, which is a singularly permanent substance. Blot over a printed page with common writing ink, wash it with chloride of lime, when the blots will disappear, and leave the printing unchanged.

INFLUENCE OF COLOURED GLASS ON BULBOUS ROOTS.

Put a bulb, as a hyacinth, narcissus, &c., into a white glass, and another into a purple glass: the latter will grow faster than the former; and, if a pinch of salt, or a piece of nitre, be put into the water whenever it is changed, the brightness of the colour of the flower will be considerably heightened.

THE SPINNING-TOP “ASLEEP.”

Spin a top, and it will for some time stand “asleep,” as it is called in the parlance of the play-ground. The cause is thus explained by Dr. Arnot, in his valuable Elements of Physics: “While the top is perfectly upright, its point being directly under its centre, supports it steadily, and although turning so rapidly, has no tendency to move from the place; but, if the top incline at all, the side of the peg, instead of the very point, comes in contact with the floor, and the peg then becomes a little wheel or roller, advancing quickly, and, with its touching edge, describing a curve somewhat as a skater does, until it becomes directly under the body of the top, as before. It thus appears that the very fact of the top inclining causes the point to shift its place, so that it cannot rest until it come again directly under the centre of the top.”

TO JUDGE OF WEIGHTS.

Persons accustomed to estimate weights by poising them in their hands, will distinguish perfectly between two, only differing by a thirtieth part. In comparing two weights, poise one and then instantly the other, in the same hand; the few seconds of time that pass between the poising of the two weights will not prevent their accurate comparison. The interval may amount to twenty seconds, yet a just estimate may still be made; but when it amounts to forty seconds, all accuracy will be lost.

QUICKSILVER AND OIL UNITED.

Let fall a very small drop of oil upon a large drop of mercury, and the latter will become enlarged. This phenomenon is attributed to a combination of the oil with the mercury, which produces a compound, the attraction of which is less strong than that of pure mercury.

TO DISSOLVE THE SODA IN GLASS.

Glass consists of sand, carbonate of soda, and red lead, heated together. If water be poured into a glass vessel, neither of the ingredients will be affected by it; but, if the glass be reduced to a fine powder, and water be poured on it, the soda will instantly be dissolved.

Or, moisten, with water a piece of tumeric, or test-paper, drop on it a little powdered glass, and the soda in it will change the yellow paper to brown.

WATERPROOF PAPER.

Make a solution of caoutchouc in caoutchoucine, plunge into it, once or twice, unsized paper, and dry it by a gentle heat. It may then be used as writing paper, and will resist all humidity; and small vessels made of it will even contain water.

TO DISSOLVE GOLD OR PLATINUM.

Mix a little nitric acid with half the quantity of muriatic acid, into which put the metal for solution.

Or, pour a little aqueous solution of chlorine into a small glass, and put in a bit of pure gold leaf; stir it with a glass rod, and the gold will dissolve. Thus gold, which cannot be dissolved in nitric, sulphuric, or other strong acids, will quickly disappear in water, with a little chlorine in solution.

COLDER THAN ICE.

Mix common salt with pounded ice or snow, and they will run into brine, which will be much colder than the ice or snow.

CONTRA-CRYSTALLIZATION.

Dissolve two ounces of nitre and three of Glauber salts in five ounces of warm water; fill two bottles with the solution, into one of which put a crystal of nitre, and into the other a crystal of Glauber salts; place both bottles in ice-cold water, when nitre only will crystallize in the one and Glauber salts in the other.

ONE AND ONE DO NOT MAKE TWO.

Mix a wine-glass full of sulphuric acid with a wine-glass full of water, cautiously; and, on re-measuring the mixture, it will not be found sufficient to re-fill both glasses.

TO COPY WRITING INSTANTLY.

Add a little sugar to ink, with which write the letter to be copied; then lay a sheet of thin unsized paper, damped with a sponge, on the writing; pass lightly over it a flat iron, very moderately heated, and a reverse impression of the writing will be accurately taken off.

THE RIVAL DIALS.

Fix two pendulum clocks to the same wall, or lay two watches upon the same table, and they will take the same rate of going, though they would vary in that rate if they were placed in separate apartments. Indeed, it has been observed, that the pendulum of one clock will even stop that of the other, and that the stopped pendulum will, after a certain time, go again, and, in its turn stop the other pendulum.

TO SPIN INDIAN RUBBER.

Dissolve a small piece of Indian rubber in a little caoutchoucine, and put a drop or two of the solution upon a looking-glass or window-pane; touch it lightly with a dry piece of Indian rubber, quickly draw out a fine thread, which attach to a card, and wind off as silk.

INDELIBLE WRITING.

As the art of man can unmake whatever his ingenuity can make, we have no right to expect an indelible ink; however, an approximation to it may be made as follows: make a saturated solution of indigo and madder in boiling water, in such proportions as to give a purple tint; add to it from one-sixth to one-eighth of its weight of sulphuric acid, according to the thickness and strength of the paper to be used. Write with this ink, and expose the paper to a gradual heat from the fire, when the characters will be completely black, the letters being burnt in and charred by the sulphuric acid. If the acid has not been used in sufficient quantity to destroy the texture of the paper, and reduce it to the state of tinder, the colour may be discharged by washing it with a strong solution of oxalic acid in water. When the full proportion of acid has been employed, crumple and rub the paper, and the charred letters will fall out; then by placing a black ground behind the letters, they may be preserved, and thus a species of indelible writing may be procured, the letters being, as it were, stamped out of the paper.

VEGETABLE ANATOMY.

Soak any part of a plant in nitric acid for a short space of time, and all power of cohesion will be lost by the vessels, which will become transparent, and be easily separable from each other by gentle dissection. So complete will be the effect, that even the most delicate cells of the cellular tissue will become disengaged from each other, and may be examined singly with perfect ease. This discovery will enable persons who have not compound microscopes, and delicate directing instruments, to anatomize plants with facility.

TO TELL WHAT O’CLOCK IT IS BY THE MOON.

This may be calculated by the shadow which the moon casts upon a sun-dial, it being only necessary to know the moon’s age, which may be found in an almanack. If the new moon happens in the morning, this day is taken into the account; but if it happens after noon, the following day is counted the first. The moon’s age is to be multiplied by four and divided by five. The quotient must either be added to the hour, which the shadow indicates on the sun-dial, and the sum will give the time sought; or subtract from the quotient the hour shown by the moon upon the dial, and the remainder will give the hour sought. The first is to be done when the shadow falls on an hour of the afternoon, and the latter when it falls upon an hour of the forenoon. The following are examples:

1st. Suppose the moon to be ten days old, and the shade cast by the moon upon the sun-dial to be at half-past two; or, that the shadow cast by the moon falls on the place at which the shadow cast by the sun stands at half-past two;—what o’clock was it then? The answer is calculated as follows:—The moon’s age, 10 days × 4 = 40 40/5 = 8. Eight, therefore, is the time when the moon was in the meridian, and 8 + 2½ = 10½, or half-past ten, the hour sought.

2d. Suppose the moon to have been 18 days old, and the shadow cast by it on the sun-dial to have marked eleven. This time is subtracted from the hour when the moon was in the meridian on that day, and from which the hour marked by the shadow must be deducted. The shadow shows here 11 o’clock in the forenoon, or one hour before noon, which, deducted from 2h. 24m. gives 1h. 24m.; 2? - 1 = 1?, or 24 minutes past one o’clock.

THE PHYSIOGNOTYPE.

This is a newly-invented instrument, by the aid of which a person may have a plaster cast of his face taken without submitting to the usual unpleasant process.

It consists of an assemblage of very fine moveable wires, confined closely together within a broad hoop or band, after the manner of the bristles in a telescope hearth-brush, but not closed at the back, in order to allow to the wires a free passage. The wires slide in a metal plate, perforated all over with holes, very fine and close together. The apparatus is surrounded by an outer case which is filled with warm water, in order to prevent any unpleasant sensation on the contact of the instrument with the skin.

When it is desired to take a likeness, the instrument is applied to the face with a gentle and gradual pressure, the wires easily yield and slide back, conformably to the prominences of the countenance; they are then fixed tightly in their position, and thus form a mould which will yield a perfect and faithful cast of the face, in which even the most minute line will appear with the strictest accuracy.

INFINITE DIVISIBILITY OF MATTER.

Dissolve a single grain of copper in about one dram of nitric acid, and dilute the solution with about one ounce of water, when it will be evident that a single drop of the mixture must contain an almost immeasurably small portion of copper. Yet, if the blade of a knife be dipped into it, it will become covered with a coat of copper; thus showing that the copper can be infinitely divided without any alteration in its properties.

HOLDING THE BREATH.

If a person inspire deeply, he will be able, immediately after, to hold breath for a time, varying with his health, state of exertion, or repose. A man, during an active walk, may not be able to cease breathing for more than half a minute; but, after resting on a chair or bed, he may refrain from breathing for a minute and a half, or even two minutes. But if he will prepare himself by breathing deeply, hardly, and quickly (as he would naturally do after running), and ceasing that operation with his lungs full of air, then hold his breath as long as he is able, he will find that the time, during which he can remain without breathing, will be double, or even more than double the former. This effect may be rendered exceedingly serviceable, as on many occasions a man who can hold breath for a minute, or two minutes, may save the life of another; such as in entering a chamber on fire, rescuing from drowning, &c.

SAND IN THE HOUR-GLASS.

It is a remarkable fact, that the flow of sand in the hour-glass is perfectly equable, whatever may be the quantity in the glass; that is, the sand runs no faster when the upper half of the glass is quite full than when it is nearly empty. It would, however, be natural enough to conclude that, when full of sand, it would be more swiftly urged through the aperture, than when the glass was only a quarter full, and near the close of the hour.

The fact of the even flow of sand may be proved by a very simple experiment. Provide some silver sand, dry it over or before the fire, and pass it through a tolerably fine sieve. Then take a tube, of any length or diameter, closed at one end, in which make a small hole, say the eighth of an inch; stop this with a peg, and fill up the tube with the sifted sand. Hold the tube steadily, or fix it to a wall, or frame, at any height from a table; remove the peg, and permit the sand to flow in any measure for any given time, and note the quantity. Then, let the tube be emptied, and only half or a quarter filled with sand, measure again, for a like time, and the same quantity of sand will flow: even if you press the sand in the tube with a ruler or stick, the flow of the sand through the hole will not be increased.

The above is explained by the fact, that when the sand is poured into the tube, it fills it with a succession of conical heaps, and that all the weight which the bottom of the tube sustains, is only that of the heap which first falls upon it; as the succeeding heaps do not press downward, but only against the sides or walls of the tube.

RESISTANCE OF SAND.

From the above experiment it may be concluded, that it is extremely difficult to thrust sand out of a tube by means of a fitting plug or piston; and this, upon trial, is found to be the case. Fit a piston to a tube (exactly like a boy’s pop-gun), pour some sand in, and try with the utmost strength of the arm to push out the sand. It will be found impossible to do this: rather than the sand should be shot out, the tube will burst at the sides.

GLASS BROKEN BY SAND.

If bullets be let fall on glass which has been cooled in the open air, they will not break it; but, if a few grains of sand be let fall on the same kind of glass, it will be broken into a thousand pieces! This is explained by the lead not scratching the surface of the glass; whereas the sand, being sharp and angular, scratches sufficiently to break it.

TO BLEACH IVORY.

Place any piece of discoloured ivory beneath a glass, expose it to the sun, and it will soon be restored to pure whiteness; whereas, if the ivory be exposed to the sun without the glass covering, it will become more discoloured.

VANISHING SHELLS.

Put into a little diluted muriatic acid, a common whelk-shell, when it will be completely dissolved, and not a sensible trace of it left behind.

If an oyster-shell, or land snail-shell be put into the acid, their substances will disappear, but the form or skeleton of the shells will remain.

THE MAGIC EGG.

Fill a basin with dilute muriatic acid, and put into it an egg, which will sink; but, in a few seconds, the whole of the egg-shell being covered with bubbles of carbonic acid gas, will rise to the surface, a portion of the egg will be lifted above the surface, and the whole egg will slowly rotate. This rotation is formed by the bubbles of gas forming at the under part of the egg, and over all the submersed portions, which render them lighter than the portions above the liquid level, till the under portion ascends and the other descends.

THE MAGIC WHIRLPOOL.

Fill a glass tumbler with water, throw upon its surface a few fragments or thin shavings of camphor, and they will instantly begin to move and acquire a motion, both progressive and rotatory, which will continue for a considerable time. During these rotations, if the water be touched by any substance which is at all greasy, the floating particles will quickly dart back, and, as if by a stroke of magic, be instantly deprived of their motion and vivacity.

In like manner, if thin slices of cork be steeped in sulphuric ether in a closed bottle, for two or three days, and then placed upon the water, they will rotate for several minutes, like the camphor; until the slices of cork having discharged all their ether, and become soaked with water, they will keep at rest.

If the water be made hot, the motion of the camphor will be more rapid than in cold water, but it will cease in proportionately less time. Thus, provide two glasses, one containing water at 58 degrees, and the other at 210 degrees; place raspings of camphor upon each at the same time; the camphor in the first glass will rotate for about five hours, until all but a very minute portion has evaporated, while the rotation of the camphor in the hot water will last only nineteen minutes; about half the camphor will pass off, and the remaining pieces, instead of being dull, white, and opaque, will be vitreous and transparent, and evidently soaked with water. The gyrations, too, which at first will be very rapid, will gradually decline in velocity, until they become quite sluggish.

The stilling influence of oil upon waves has become proverbial: the extraordinary manner in which a small quantity of oil instantly spreads over a very large surface of troubled water, and the stealthy manner in which even a rough wind glides over it, must have excited the admiration of all who have witnessed it.

By the same principle, a drop of oil may be made to stop the motion of the camphor as follows: throw some camphor, both in slices and in small particles, upon the surface of water, and while they are rotating, dip a glass rod into oil of turpentine, and allow a single drop thereof to trickle down the inner side of the glass to the surface of the water; the camphor will instantly dart to the opposite point of the liquid surface, and cease to rotate. If a piece of hard tallow or lard be employed, the motion of the camphor will be more slowly stopped than by oil or fluid grease, as the latter spreads over the surface of the water with greater rapidity.

If a few drops of sulphuric or muriatic acid be let fall into the water, they will gradually stop the motion of the camphor; but, if camphor be dropped into nitric acid diluted with its own bulk of water, it will rotate rapidly for a few seconds and then stop.

If a piece of the rotating camphor be attentively examined with a lens, the currents of the water can be well distinguished, jetting out, chiefly from the corners of the camphor, and bearing it round with irregular force.

The currents, as given out by the camphor, may also be seen by means of the microscope; a drop or two of pure water being placed upon a slip of glass, with a particle of camphor floating upon it. By this means, the currents may be detected, and it will be seen that they cause the rotations.

Or, a flat watch-glass, called a lunar, may be employed, raised a few inches, and supported on a wire ring, kept steady by thrusting one end into an upright piece of wood, like a retort stand. Then put the camphor and water in the watch-glass, and place under the frame a sheet of white paper, so that it may receive the shadow of the glass, camphor, &c., to be cast by a steady light placed above, and somewhat on one side of the watch-glass. On observing the shadow, which may be considered a magnified representation of the object itself, the rotations and currents can be distinguished.[B]

MAGIC PORCELAIN.

A peculiar kind of porcelain was formerly manufactured in China, which exhibited its colour and devices only when filled with water. Though the art of manufacturing this porcelain has been lost, and the mode cannot now be described with accuracy, the following has been conjectured as not very remote from the truth. The first requisite was that the vessel be extremely thin, so that the figures to be formed might be sufficiently clear and perceptible. After the vessel has been baked, the figures, which were mostly fish, (as those were most appropriate with the water), were formed on the inside; and, after the colour had dried, a second extremely thin coat, of the same substance as that of which the vessel was constructed, was lain on the inside and varnished. The fish, or other device, would then, it is evident, be enclosed between the two coats of the ware of which the vessel was made. All that remained to be done was to grind the outside of the vessel as close to the figures as possible, to varnish it again, and bake it a second time; and though, after this operation, the figures and embellishments would not be at all perceptible, yet, so soon as the vessel was filled with water, they would at once be rendered clear and distinct to a degree scarcely credible. Attempts have been made to revive this beautiful art, but hitherto without success.

A GALVANIC TONGUE.

Coat the point of the tongue with tin-foil, and its middle part with gold or silver leaf; when a sourish taste will be produced, and the tongue will be galvanised.

DRINKING PORTER OUT OF PEWTER.

If porter be drunk out of a pewter pot, it will produce a more brisk sensation than when it is taken out of a glass vessel, which is ascribed to a galvanic effect. In this instance there is a combination of one metal and two dissimilar fluids, which combination constitutes a galvanic circle. In the act of drinking, one side of the pewter pot is exposed to the action of the saliva, which moistens the lip, while the other metallic side is in contact with the porter; the circuit being thus completed, an agreeable relish is communicated to the beverage when it comes in contact with the tongue.

ELECTRIC OR GALVANIC PRESERVATION.

Immerse a slip of copper in dilute nitric acid, and it will be soon corroded and dissolved; but, if a slip of zinc be immersed with the copper, the zinc will be dissolved, and the copper remain unaltered and uninjured.

LIGHT FROM THE DIAMOND.

Expose a fine diamond to the sunbeams, and carry it into a dark room, when it will exhibit phosphorescence: and it has been stated that such diamonds as do not display this peculiarity, may be made to do so by dipping them into melted borax.

The diamond becomes phosphorescent also when fixed to the prime conductor of an electrical machine, and a few sparks may be taken from it. It likewise becomes electric by friction; and the Hon. Mr. Boyle obtained electric gleams by rubbing two diamonds together in the dark.

TO BREAK A STONE WITH A BLOW OF THE FIST.

Select two stones from three to six inches long, and about half as thick; lay one flat on the ground, on which place one end of the other, raising the reverse end to an angle of forty-five degrees, and just over the centre of the stone (with which it must form a T,) supporting it in that position by a piece of thin twig or stick, one, or one and a half inch long; if the raised stone be now smartly struck about the centre, with the little finger side of the fist, the stick will give way, and the stone will be broken to pieces: the stones must be laid so as not to slip, otherwise the experiment will fail.

MIMIC FROST-WORK.

Fasten a sprig of fresh rosemary, or any similar shrub, to the inside of a small bandbox, near the top; heat a thick tile, and sprinkle it with gum benzoic, and immediately place the bandbox over it, when the acid will be sublimed by the heat, and will condense in a white vapour upon the green plant, giving it the appearance of being covered with hoarfrost.

TO MELT LEAD IN A PIECE OF PAPER.

Wrap up a very smooth ball of lead in a piece of paper, taking care that there be no wrinkles in it, and that it be everywhere in contact with the ball; if it be held in this state, over the flame of a taper, the lead will be melted without the paper being burnt. The lead, indeed, when once fused, will not fail in a short time to pierce the paper, and run through.

HYDROSTATIC BALANCE.

Provide a pair of scales, in one of which place a tumbler filled with water, and poise it by placing weights in the opposite scale; then hold in the tumbler a block of wood, or any substance nearly the size of the tumbler, but so that it shall not touch the sides or bottom; when, although nearly the whole of the water will have to run over the sides, and only a spoonful may remain, the scales will continue balanced; and all this without regard to the weight of the body you plunge into the water, taking care to hold it entirely clear of the tumbler, so that it touch it nowhere; for the effect will be the same if what you plunge in be scooped hollow and made water-tight. A bladder blown up, tied fast, and held down in the water, so as to leave only a spoonful of water surrounding it, will keep the scales balanced just as well as a block of lead of the same size.

METALLIC REDUCTION.

Mix a little red lead with some powdered charcoal, and with the mixture fill the bowl of a tobacco-pipe; set it over a common fire, and in about twenty minutes the lead will be found reduced to its metallic state.

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