This design was by Mr. Joseph Paxton, and resembled in its general form the building as it is now executed, with the exception of the transept and semicircular roof, which were subsequently added, and were suggested by Mr. Barry.

The result of the tenders appears to have been unfavourable to the Committee's design; and in their Report to the Royal Commission on the subject, made a few days afterwards, they proposed to omit the great dome and some portions of the design which were not essential, by which they considered that the cost of its execution might be reduced below 100,000l.; at the same time, they made special mention of Mr. Paxton's design, which, however, they considered would prove more expensive.

Mr. Paxton's design had been brought before the public before this period; for, considering that his best road to success would be to get a favourable verdict from that many-headed jury, he published a view and description of it in the Illustrated News, and, through the influence of Mr. Stephenson, he got his plans laid before the Royal Commission, in consequence of which he obtained an interview with his Royal Highness the President. The encouragement given him by the attention bestowed upon his design by the Royal Commission, and the favourable opinion of the public, had determined him to procure a tender for the execution of the work, to be sent in with those upon the Committee's design. This he was enabled to do by the great energy and promptitude of the contractors, Messrs. Fox and Henderson, to whom he applied at the eleventh hour. The difficulties that had to be overcome, owing to the shortness of the time remaining for the estimates to be made up, can scarcely be better laid before the reader than they have been by an able writer in "Household Words:"—

"It was now Saturday, and only a few days more were allowed for receiving tenders. Yet before an approximate estimate of expense could be formed, the great glass-manufacturers and iron-masters of the north had to be consulted. This happened to be dies mirabilis the third; for it was the identical Saturday on which the Sunday postal question had reached its crisis, and there was to be no delivery the next day! But in a country of electric telegraphs, and of indomitable energy, time and difficulties are annihilated; and it is not the least of the marvels wrought in connexion with the great edifice that, by aid of railway-parcels and the electric telegraph, not only did all the gentlemen summoned out of Warwickshire and Staffordshire appear on Monday morning at Messrs. Fox and Henderson's office, in Spring Gardens, London, to contribute their several estimates to the tender for the whole, but within a week the contractors had prepared every detailed working-drawing, and had calculated the cost of every pound of iron, of every inch of wood, and of every pane of glass.

"There is no one circumstance in the history of the manufacturing enterprise of the English nation which places in so strong a light as this its boundless resources in materials, to say nothing of the arithmetical skill in computing at what cost and in how short a time those materials could be converted to a special purpose. What was done in those few days? Two parties in London, relying on the accuracy and good faith of certain iron-masters, glass-workers in the provinces, and of one master-carpenter in London, bound themselves for a certain sum of money, and in the course of some four months, to cover eighteen acres of ground with a building upwards of a third of a mile long, and some four hundred and fifty feet broad. In order to do this, the glass-maker promised to supply, in the required time, nine hundred thousand square feet of glass (weighing more than four hundred tons), in separate panes, and these the largest that ever were made of sheet glass; each being forty-nine inches long. The iron-master passed his word in like manner to cast in due time three thousand three hundred iron columns, varying from fourteen feet and a half to twenty feet in length: thirty-four miles of guttering-tube, to join every individual column together under the ground; two thousand two hundred and twenty-four girders (but some of these are of wrought iron); besides eleven hundred and twenty-eight bearers for supporting galleries. The carpenter undertook to get ready within the specified period two hundred and five MILES of sash-bar, flooring for an area of thirty-three millions of cubic feet, besides enormous quantities of wooden walling, louvre-work, and partition.^[3]

"It is not till we reflect on the vast sums of money involved in transactions of this magnitude that we can form even a slight notion of the great, almost ruinous loss, a trifling arithmetical error would have occasioned, and of the boundless confidence the parties must have had in their resources and in the correctness of their computations. Nevertheless, it was one great merit in Mr. Paxton's original details of measurement that they were contrived to facilitate calculation.

"There was little time for consideration, or for setting right a single mistake, were it ever so disastrous. On the prescribed day the tender was presented, with whatever imperfections it might have had, duly and irredeemably sealed. But after-checkings have divulged no material error."

The Royal Commission appear from the first to have been favourably impressed with Mr. Paxton's design, partly, no doubt, because its adoption would at once silence the great bricks-and-mortar objection to the occupation of the site in Hyde Park; and the result was that, on the 16th of July, Messrs. Fox and Henderson's tender of 79,800l. for Mr. Paxton's design was verbally accepted, and, as soon as the necessary arrangements could be made, the contract was formally concluded.

AS Mr. Paxton himself has stated, the design for a building of such magnitude could not have been produced in so short a space of time without the aid of the experience he had gained in constructing other great buildings of a somewhat similar character; the progress of this experience Mr. Paxton has described in the lecture he delivered to the Society of Arts on the 13th of November, 1850, from which we have made the following extracts; and we hope to be excused by the reader for their copiousness, on the ground that no man can so well relate his own doings as the actor himself:—

"The Great Industrial Building now in the course of erection, and which forms the subject of the present paper, was not the production of a momentary consideration of the subject. Its peculiar construction, in cast-iron and glass, together with the manner of forming the vast roof, is the result of much experience in the erection of buildings of a similar kind, although on a smaller scale, which has gradually developed itself through a series of years. It may not, therefore, be uninteresting to give a brief account of the reasons which led me to investigate the subject of glass roofs and glass structures generally, and which have resulted in the Exhibition Building.

"In 1828, when I first turned my attention to the building and improvement of glass structures, the various forcing-houses at Chatsworth, as at other places, were formed of coarse thick glass and heavy woodwork, which rendered the roofs dark and gloomy, and, on this account, very ill suited for the purposes they were intended to answer. My first object was to remove this evil, and, in order to accomplish it, I lightened the rafters and sash-bars, by bevelling off their sides; and some houses which were afterwards built in this manner proved very satisfactory. I also at this time contrived a light sash-bar, having a groove for the reception of the glass; this groove completely obviated a disadvantage connected with the old mode of glazing, namely, the putty becoming continually displaced by sun, frost, and rain, after the sashes had been made for a short time, and the wet by this means finding its way betwixt the glass and the wood, and producing a continual drip in rainy weather.

"About this period the desire for metallic roofs began to extend in every direction; and as such structures had a light and graceful appearance, it became a question of importance as to the propriety of using metal sashes and rafters, instead of wooden ones, for horticultural purposes. After carefully observing the effects of those built by various persons, it became apparent to me that the expansion and contraction of metal would always militate against its general adoption, as at no season of the year could the sashes and rafters be made to fit.

"The extra expense, also, of erecting metallic-roofed houses was a consideration. In 1833 I contemplated building a new range of hot-houses; and being desirous of knowing how much they would cost, if erected of metal, a plan of the range was prepared and sent to Birmingham, and another to Sheffield, with a desire to be furnished with estimates for that purpose. The estimate from Birmingham was 1,800l.; and the other, from Sheffield, was 1,850l. These appeared to me such enormous sums, that I at once set about calculating how much the range would cost if built of wood under my own inspection; and the result was, that I was able to complete the whole range, including masonry (which was omitted in the metal estimates), for less than 500l.

"Besides the extra cost of metallic roofs, we must add the extreme heat of such houses in hot weather, and their coldness in times of frost; the liability to breakage of glass from expansion and contraction of the metal; the very limited duration of the smaller portions, as sash-bars, from corrosion, by exposure to the alternations of heat, cold, and moisture, inseparable from gardening operations, and which could only be prevented by making use of the expensive material, COPPER; and the difficulty, when compared with wood, of repairing any damages, as a wooden roof could at any time be set to rights by a common carpenter. These different items formed in my mind so many objections to its use, and the same disadvantages soon became generally apparent.

"It was now thought advisable by some parties that, in order to obviate the many disadvantages in the use of metal, the rafters and frame-work of the sashes ought to be made of wood, and the sash-bars of metal. This plan certainly presented more advantages than the other, yet it was quite obvious that materials so incongruous could never give satisfaction; and accordingly, in a few years, as I had anticipated, the rage for these structures gradually subsided, and the use of wood again became resorted to by most persons, as the best material for horticultural purposes.

"In the construction of glass-houses requiring much light, there always appeared to me one important objection, which no person seemed to have taken up or obviated; it was this. In plain lean-to or shed roofs, the morning and evening sun, which is on many accounts of the greatest importance in forcing fruits, presented its direct rays at a low angle, and, consequently, very obliquely to the glass. At those periods most of the rays of light and heat were obstructed by the position of the glass and heavy rafters, so that a considerable portion of time was lost both morning and evening; it consequently became evident that a system by which the glass would be more at right angles to the morning and evening rays of the sun would obviate the difficulty, and remove the obstruction to rays of light entering the house at an early and late hour of the day.

"This led me to the adoption of the ridge-and-furrow principle for glass roofs, which places the glass in such a position that the rays of light in the mornings and evenings enter the house without obstruction, and present themselves more perpendicularly to the glass at those times when they are the least powerful; whereas at mid-day, when they are most powerful, they present themselves more obliquely to the glass. Having had this principle fixed in my mind, and being convinced of its importance, I constructed a pine-house in 1833 as an experiment, which still exists unimpaired, and has been found fully to answer the purpose.

"In 1834 I resolved to try a further experiment on a larger scale, on the ridge-and-furrow principle, in the construction of a green-house of considerable dimensions, which also remains and answers admirably. For this building I made a still lighter sash-bar than any I had previously used; on which account the house, when completed (although possessing all the advantages of wood), was as light as if constructed of metal. The whole length of this structure is 97½ feet, and its breadth 26 feet; the height at the back is 16 feet 9 inches, and in the front 12 feet 3 inches. A span so large as 26 feet could not be safely covered with a roof constructed in the ordinary way, unless the sash-bars were stronger, and the assistance of heavy rafters and numerous supports was afforded. The house presents a neat and light appearance, and consists of 15 bays, and pediments in front, supported by 16 slender reeded cast-iron columns. Whilst it makes an admirable green-house, it is also an economical building; for, at the period of its construction, notwithstanding the heavy tax on glass (since removed), it only cost at the rate of twopence and a fraction per cubic foot. At the present time, considering the change in the price of material, and the removal of the glass-tax, it could be constructed at a considerably smaller amount.

"Having in contemplation the erection of the Great Conservatory in its present form, it was determined, in 1836, to erect a new curvilinear hot-house 60 feet in length and 26 feet in width, with the elliptical roof on the ridge-and-furrow principle, to be constructed entirely of wood, for the purpose of exhibiting how roofs of this kind could be supported. The plan adopted was this: the curved rafters were composed of several boards securely nailed together on templets of wood cut to the exact curve; by this means a strength and firmness were obtained sufficient to support an enormous weight.

"In 1837 the foundations of the Great Conservatory were commenced; and in constructing so great a building it was found desirable to contrive some means for abridging the great amount of manual labour that would be required in making the immense number of sash-bars requisite for the purpose. Accordingly, I visited all the great workshops in London, Manchester, and Birmingham, to see if anything had been invented that would afford the facilities I required. The only apparatus met with was a grooving-machine, which I had at once connected with a steam-engine at Chatsworth, and which was subsequently so improved as to make the sash-bar complete.

"For this apparatus the Society of Arts, in April, 1841, awarded me a medal; and this machine is the type from which all the sash-bar machines found in use throughout the country at the present time are taken. As the Conservatory was erected under my own immediate superintendence, I am able to speak accurately as to the advantages of the machine: it has, in regard to that building alone, saved in expenses 1,400l. The length of each of the bars of the Conservatory is 48 inches; only one inch shorter than those of the Exhibition Building. The machine was first used in its present form in August, 1838; and its original cost, including table, wheels, and everything complete, was 20l. The motive power is from a steam-engine employed on the premises for other purposes; and any well-seasoned timber may be used. The attendants required are only a man and a boy, and the expense of the power required for it when in use is comparatively trifling. The sash-bars may be made of any form, by changing the character of the saws.

"There is one particular feature in working the machine, namely, the bar is presented to the saws below the centre of motion, instead of above it (as is usual); and to the sides of the saw which are ascending from the table, instead of those which are descending. These arrangements were necessary to suit the direction of the teeth to the grain of the wood; for when the bars were presented to the saws in the usual way, the wood was crushed instead of being cut and cleaned. It is essential that the machine should revolve 1,200 times in a minute to finish the work in a proper manner.

"The glass and glazing of the Chatsworth Conservatory caused me considerable thought and anxiety, as I was very desirous to do away altogether with the numerous overlaps connected with the old system of glazing with short lengths. This old method, even under the best of management, is certain, in the course of a few years, to render unsightly any structure, however well built.

"In the course of my inquiries, I heard that Messrs. Chance and Co., of Birmingham, had just introduced from the Continent the manufacture of sheet glass. Accordingly, I went to see them make this new article, and found they were able to manufacture it three feet in length. I was advised to use this glass in two lengths, with one overlap; but to this I could not assent, as I observed, that since they had so far advanced as to be able to produce sheets three feet in length, I saw no reason why they could not accomplish another foot; and, if this could not be done, I would decline giving the order, as, at that time, sheet glass was altogether an experiment for horticultural purposes. These gentlemen, however, shortly afterwards informed me that they had one person who could make it the desired length, and, if I would give the order, they would furnish me with all I required.

"It may just be remarked here that the glass for the Exhibition Building is forty-nine inches long—a size which no country except England is able to furnish in any large quantity, even at the present day.

"In 1840 the Chatsworth Conservatory was completed and planted. The whole length of this building is 277 feet; its breadth, 123 feet over the walls; and the height, from the floor to the highest part, 67 feet.

"Notwithstanding the success which attended the erection of these buildings, it became to me a question of importance how far an extensive structure might be covered in with flat ridge-and-furrow roofs; that is, the ridge-and-valley rafters placed on a level, instead of at an inclination, as in the green-house, or curvilinear, as in the Great Conservatory. I therefore prepared some plans for an erection of the kind for the Earl of Burlington, somewhere about ten years ago; but, on account of the lamented death of the Countess, the design of erection was abandoned. However, from that time I felt assured, not only that it could be done satisfactorily, but that the most appropriate manner to form and support level glass roofs, to a great extent, was that adopted this year for the New Victoria House at Chatsworth, which may be considered a miniature type of the Great Industrial Building.

"Before describing this house, however, it may be well to notice two instances in which the flat roofs had been previously tried, and in both cases with the most perfect success.

"The first of these was a conservatory attached to a villa in Darley Dale, only a short distance from Chatsworth. This building is divided into five bays, with a glass door in the centre, and glass pilasters separating the bays; the ridge-and-furrow roof covers an opening of seventeen feet in the clear. The ventilation is simultaneously effected by a lever connected with a rod, which is attached to all the ventilators....

"The second instance is this. In the spring of 1848, plans were prepared for the erection of an ornamental glass structure, to cover the conservatory wall at Chatsworth. This wall was previously a plain flued structure, devoted to the growth of rare and choice plants. The new erection is 331 feet in length, and 7 feet in width. It is divided into ten bays, with an ornamental centre projecting beyond the general line of the building. Each bay is subdivided by smaller bays, which are separated by glass pilasters; the glass sashes are so arranged that they can be removed in summer, and the whole thrown open to the gardens, whilst in winter the building affords an extensive promenade under cover. The ground on which this structure is built has a fall of 25 feet 6 inches in its whole length; consequently, there is a proportionate fall at each bay, which gives great variety, and obviates the monotony that would be exhibited in a building of such length and dimensions placed on a uniform level. The lower side of each bay is finished by a glass pilaster, three feet in width, and surmounted by a vase on the wall behind. The roof is on the ridge-and-furrow principle, with the rafters on a very slight inclination; and the ventilation is effected in a similar but more perfect manner than that already described as in use at the conservatory at Darley Dale.

"The new Victoria Regia House, which presents a light and novel appearance, is 60 feet 6 inches in length, and 46 feet 9 inches in breadth. Although, when compared with the Great Industrial Building, the Victoria House is a very diminutive structure, yet the principles on which it is constructed are the same, and may be carried out to an almost unlimited extent. The form of the roof, the general elevation, the supports, and the mode of construction, are all quite simple, and yet fully answer the purposes for which they were intended.

"The Victoria House, however, was so built as to retain as much moisture and heat as possible, and yet to afford a strong and bright light at all seasons; whilst, on the contrary, the Industrial Building, being intended to accommodate a daily assemblage of many thousands of individuals, and a vast number of natural and mechanical productions, many of which would be destroyed by moisture and heat, is constructed so as fully to answer that end."

This, then, was the experience which enabled Mr. Paxton to conceive his design for the "Crystal Palace," a description of which as it has subsequently been carried out we must now proceed with.

THE plan forms a parallelogram, 1,848 feet long and 408 feet wide, besides a projection on the north side, 48 feet wide and 936 feet long. A main avenue, 72 feet wide and 66 feet high, occupies the centre through the whole length of the building. Flanking this on either side are smaller avenues alternately 24 feet and 48 feet wide; the two first on either side of the centre are 43 feet, and the remainder 23 feet high. About the centre of the entire length, at a point determined by the position of a row of large trees, which it was resolved to inclose, these avenues are crossed by a transept of the same width as the main avenue, or 72 feet, and 108 feet high; two other groups of trees on the ground give occasion for open courts, which are inclosed within the building. The area thus inclosed and roofed over amounts to no less than 772,784 square feet, or about 19 acres;^[4] the building is, therefore, about four times the size of St. Peter's at Rome, and more than six times that of St. Paul's, London. Three entrances lead to this vast interior, one in the centre of the principal or south front, and one at either end of the building. The number of these is necessarily small, in order to facilitate the arrangements for the money-taking, and to avoid having too large a staff of officers; on the other hand, it was equally desirable to afford the most ample opportunities of egress for visitors, and accordingly fifteen exit doors are placed at frequent intervals.

GROUND-PLAN OF THE BUILDING.

It will be well to mention here that the horizontal measure of 24 feet, which we have seen as the unit in the plan of the Building Committee, is also preserved in the present plan; every horizontal dimension of which is either a certain number of times or divisions of twenty-four feet.

The avenues into which the plan is divided are formed by hollow cast-iron columns twenty-four feet apart, which rise in one, two, and three storeys respectively, to support the roof at the different heights given above; in the lower storey these columns are nineteen feet high, and in the two upper ones seventeen feet. Between the different lengths of the columns short pieces are introduced, called "connecting-pieces," from the office they perform; these are three feet long, and are so contrived that they serve to support girders in horizontal tiers, dividing the greatest height into three storeys as already mentioned. The girders, of which some are of cast and some of wrought iron, are all of the same depth, namely, three feet, with the exception of four, to be specially named hereafter, and by this arrangement the same horizontal lines are preserved throughout the whole of the building. They are also all similar in appearance, forming a kind of lattice-work, by which construction they do not look too heavy for the slight supports; and large solid masses are avoided, practically showing how great strength may be combined with elegance and lightness. The first or lower tier of these girders, in parts of the building more than one storey in height, forms the support for the floor of the galleries, which are twenty-four feet wide, and extend the whole length of the building in four parallel lines, intercepted only by the transept, round the ends of which they are continued. Numerous cross galleries connect each pair of longitudinal lines on either side of the centre avenue, which remains uninterrupted from end to end, and can only be crossed on the gallery-floor at the extremities.

These galleries are reached by eight double staircases, of easy ascent and ample width, which are placed between the lines of gallery so as to communicate equally readily with either, and are so distributed as to give two to each quarter of the building; in the eastern or foreign half two supplementary staircases of smaller dimensions have been added.

In those parts of the building more than two storeys in height, the second horizontal tier of girders does not support a gallery, but serves only to give stiffness to the columns. The upper tier of girders, in all cases, supports the roof, which is one of the most peculiar features in the structure. In its general form the roof is flat; but it is made up of a series of ridges and furrows, the rise and fall of which is but small, and is thus arranged: the roof-girders or trusses being twenty-four feet apart, and lying in the transverse direction of the building, the space between them is spanned by light beams or rafters, which are cambered or bent upwards, and are hollowed out in a groove on the top to form a gutter. The rafters are placed eight feet apart, their ends resting on the roof-girders, and lying, therefore, in the opposite direction to them, that is, in the direction of the length of the building; these rafters are commonly called the Paxton's Gutters. Between the rafters so described, ridges are supported by light sash-bars sloping up to them, at an inclination of two-and-a-half to one, and the rafter itself forms the bottom of the furrow. The advantage of this form of roofing is the facility it affords for the escape of the water, which runs from the surface of the roof into the Paxton's gutters; from them it is discharged into the main gutters resting on the roof-girders, by which it is conducted to the hollow columns, and passes down through them into the drains. A drop of water falling on the most distant point from the discharge would only have to traverse a distance of forty-eight feet; but in most cases the length to be passed over before reaching the down pipe would be considerably less.^[5] The covering of the roof is glass, fixed between the sash-bars, which are grooved to receive it; and in order to carry off the moisture arising from condensation on the inner surface of the glass, the rafters have a small groove on each side, which makes the Paxton's gutter complete, and from which the moisture is also discharged into the main gutters. The essential portions of the roof may therefore be considered as a network of gutters; one set, the main gutters, lying in a transverse direction, and the others resting on them, and lying in the direction of the length of the building; by which arrangement any amount of surface can always be covered by roofing of a small span. The principle is precisely the same as that of subdividing large fields of arable land into strips or "lands" with furrows between them, in order to facilitate the surface-drainage.

The outer inclosure, on the ground-floor, is formed by dividing each 24-feet bay between the columns into three 8-feet bays by half columns of wood, between which is placed boarding, held in its place by iron clips and bolts; a plinth, four feet high, is formed immediately above the floor by frames, filled with what are commonly called louvre-blades, which are hung on pivots, and of which a large number can be moved simultaneously for the admission of air; similar ventilating-frames, three feet deep, are introduced at the top of each storey round the entire circuit of the building, and by this means a ventilating-surface of no less than 40,800 square feet is obtained, or rather more than one acre.

Externally some light arches are inserted, and open panels form the inclosure for the upper louvre-frames. The details we have been describing may be readily traced in the engraving of a portion of the lower storey as seen from the outside. The exit doors occupy one of the 8-feet bays opening about six feet wide. The inclosure to the upper storeys closely resembles those of the ground-floor, but glazed sashes are substituted for the close boarding, and the plinth is omitted. Each storey is crowned externally with a cornice and cresting ornament, and over the columns posts are carried up, to which flagstaffs will be fixed.

To return to the interior. The whole of the floor is boarded; that below is laid with an interval of half an inch between the boards, to allow the passage of dust from the millions of feet by which it will be trod; the gallery floor, on the contrary, has iron tongues between the boards to prevent the dust from coming through on the heads of the visitors below.

The roof of the transept, which we have described as crossing the building about the centre of its length, differs from that of the other parts, its general form being semicircular instead of flat, and rising above the rest of the building so as to show the whole of the semicircle externally. This roof is supported by arched timber ribs placed twenty-four feet apart, or one over every column, which forms a socket, into which the foot of the rib is fitted and secured by iron straps. Between the ribs, timbers are fixed which carry minor ribs at a distance of eight feet apart, and upon these the ridge-and-furrow roofing is constructed in the manner that has been described for the flat roofing, but following the curve of the arched ribs. At the springing or foot of the arch on either side of the transept there is a range of louvre-frames to assist in the ventilation of the building, and on the top of the arch externally a narrow passage is formed to give access to the different parts of this roof. On the inner side of the arch diagonal tie-rods are introduced between the main ribs, which, while they serve to increase the strength of the construction by tying together all the parts from end to end, produce an agreeable play of lines forming a kind of network over the whole of the surface.

The ends of the transept are closed in with fan-like tracery, reminding the spectator of the magnificent wheel windows of our Gothic cathedrals; this elegant feature is not visible in our interior view, but will be seen in some of the exteriors.

There is, perhaps, no part of this interesting building in which the great size and singular lightness, almost airiness, of the construction are so strikingly displayed as in the TRANSEPT, inclosing as it does a row of fine old elm-trees, as if to protect them in their venerable age from the smoke of the thousands of chimneys that have been gradually forming a destructive circle around them.

The only portion of solid untransparent roofing in the whole of this building is formed on either side of the arched roof just described, where there is a lead flat twenty-four feet wide. This was partly required for a platform to serve for carrying on the works for the arched roof, and was also exceedingly useful in giving access to the other roofs on either side; it likewise afforded the opportunity of giving some additional strength at the springing of the arched ribs to resist any possible tendency they might have to spread outwards.

An ornamental cast-iron railing designed by Mr. Owen Jones incloses the building, being placed at a distance of about eight feet from it along the principal fronts, but carried much further off at the ends, so as to inclose a considerable space, which will thus be available for exhibiting any large objects that will bear exposure to the weather, if there should not be sufficient room in the interior of the building. Gates are placed opposite all the entrances and exits, and these are so arranged that when closed they are uniform in appearance with the rest of the railing.

Having thus given a general sketch of the arrangement and appearance of the building, we shall proceed to describe somewhat more minutely the various details of the construction, of which the essential parts are few in number compared with the great repetition of each individually. To assist in this multiplied reproduction of the same form, some exceedingly ingenious machinery has been employed, which will therefore be described in connexion with the parts it has been used to form; and thus these will be traced through their various stages, from the raw material to their finished state as portions of the building. The greater part of this machinery has been used in shaping out those parts which are of wood, and particularly the different portions of the roof, with which we will therefore commence.

IT has been mentioned that the rafters which span the space between the roof-girders serve, at the same time, as gutters, for which purpose they are hollowed out on the upper face, besides having smaller grooves at the sides to take the condensation-water. The bottom of the gutter is of a circular form, which is universally considered the best for conveying liquids with the least amount of friction, and therefore the least liable to obstruction from an accumulation of dirt.

A section of the gutter, as finished, is shown. To bring it into this form, after the timbers had been sawn into the requisite general dimensions they were brought under the action of the planing-machine, where they were planed on the four sides. This machine is patented by W. Furness, of Liverpool, and was worked at the Chelsea Wharf Saw-mills. The operation was effected by cutters (a) attached to the ends of an arm revolving with great rapidity in a horizontal plane; the timbers to be planed were wedged up into a frame (b) traversing on rails, and as this was passed under the revolving cutters the upper surface was removed by them, at the same time the timbers were held down upon the frame by a large iron disc (c) pressing upon their upper surface. The disc, together with the revolving arm carrying the cutters, was capable of being adjusted vertically to the exact dimensions of the timber. The traversing-frame was slowly propelled by the machinery, and three widths of timber were operated upon at one time. On leaving the planing-machine these quarter baulks were passed on to the gutter-cutting machine. Four different cutters were required to form the section, as shown above; they were placed one behind the other, so that the piece of timber, which was presented to their action above the centre of motion, passed over each of them in succession. The first set, which revolved in a vertical plane, roughly hollowed out the larger groove to the section shown in Fig. 1; the two next were counterparts, and formed the same section in opposite directions; they were set at an inclination to the upright of about 45 degrees, the one to the right, the other to the left; and each hollowed out one of the small side grooves, and one side of the larger gutter, leaving the section of the timber respectively of the forms shown in Figs. 2 and 3. Fig. 4 shows the form of its section after it had passed both; the fourth set of cutters again revolved vertically, and gave the gutter its finished form, as shown above. As the timber passed over the cutters it was supported at the ends on revolving rollers, and was held in its place by guiding grooves, being pressed gradually forwards against the cutters.

In this manner forty-two lengths of solid gutter, each twenty-four feet and a fraction long, were completed in a day of ten hours; and as the machine was worked double time, a length of more than 2,000 feet was turned out daily ready for use: this, it has been calculated, would have required the labour of about three hundred men to be employed for the same length of time. The absolute necessity for such rapid production will be evident when it is known that no less than 110,000 feet, or about twenty miles length, of such gutters were required—very nearly the distance from Buckingham Palace to Windsor Castle.

Finished as described above, the Paxton's gutters arrived at the building, where the first operation they underwent was that of cutting them to the exact length requisite. This was a nice operation, as the smallest deviation would have caused a difficulty in fitting them into their place, and to perform it a framework was constructed by which the solid gutter could be bent to the same curve it would have when fixed; a precaution that was necessary in order that the ends might be cut off quite vertically so as to fit together when in their place. At one end of this frame-work was placed a circular saw, twenty inches diameter, hung with a pulley and balance weight, so as to be moved up and down by means of a lever. The gutter being fixed in the frame by means of hinged guage-plates, one end was cut by the circular saw being brought down upon it; and at the same time another operation was performed: two cutters, placed in the centre of the circular saw, were so arranged that when brought down upon the end of the solid gutter they cut out a semi-circular notch, so that when the ends of two gutters were afterwards placed together there was a circular hole left, through which the water passed down into the main gutter. When these operations were completed at one end of the gutter, the guage-plates were taken off, and the timber was swung round on a pivot or crutch in the centre, and the same process gone through as before; the whole scarcely occupying two minutes. We shall presently have to return to this piece of machinery, as it was also used in finishing the ridge rafters.

The solid gutter was now transferred to the hands of the carpenter, who fixed at each end, on the under-side, a small cast-iron shoe; and two struts, nine inches long, were placed so as to divide the whole length into three equal parts—the struts spread out at the top in order to present a large surface of pressure against the under-side of the gutter; and tenons projected upwards, which were fitted into mortices cut into the timber. The lower end of the struts were formed so as to give them a firm hold upon a wrought-iron rod, thirteen-sixteenths of an inch diameter, which was passed under them and through the shoes, where it was screwed up with nuts; and the struts pressing up against the timber produced the requisite bend or camber. Twenty-seven notches, to receive the sash bars, were marked with a templet and cut out on each edge of the upper-side of the gutter; and a small cast-iron plate having been fitted on the under-side at each end, the Paxton's gutter was complete and ready for fixing. The under-trussing of the rafters increased their strength considerably, so that a weight of one-and-a-half tons was required to break one which was experimented upon.

WE will next consider the sash-bars which support the ridge of the roof and receive the glass. The total length which was required of these amounts to about two hundred miles; it will, therefore, be easily understood that mechanical contrivance for cutting them out became an absolute necessity; this Mr. Paxton appears to have discovered in his works at Chatsworth, as he mentions in his lecture.

The sash-bars are one inch thick and one-and-a-half inches deep, and are grooved on each side, besides having all the four edges bevelled or chamfered; all which was done in one passage through the machine. The plank which was to form the sash-bars was passed in at one end of the machine, between pressure-rollers; it then passed between cutters placed both above and below it, which made about twelve hundred revolutions per minute, and hollowed out the different grooves; and, lastly, it passed between circular saws which divided it into separate sash-bars, after which they had only to be cut into their proper lengths.^[6] The exact length of each sash-bar when finished is four feet one inch.

In this state the skylight bars were sent to the building, where they underwent several finishing operations, necessary to make the ends fit down into the notches prepared in the ridges and gutters. Thirty of the bars were first placed together in a horizontal traversing-frame on a saw-table, on each side of which circular saws were fixed at the distance of the required length of the sash-bar; the frame was then moved forward against the saws, so that both ends of the whole set of bars were cut off simultaneously, and at the same time a cut was made at one end half-way through the bar, in order to form the shoulder against the gutter. They were then removed to another bench, where the end of the bar was bevelled and the shoulder formed by means of a small instrument having a handle with two projecting jaws fitting into the ends of the glass grooves of the bars; between these there was a small blade which, being pressed down, cut out the shoulder which had been sawn through in the other direction, and another blade was placed at the proper angle to remove the bevelled piece at the end of the bar.

One more process made the sash-bars complete for fixing—this was the drilling a hole at each end to nail them down on the gutter and ridge; and this was also done by machinery, to insure all the holes being drilled at the same angle. On one side of a horizontal bench were placed a set of four-inch driving pulleys (a a), with as many horizontal drills projecting towards the other side of the bench; a wooden traversing-plate (c) opposite each drill, and working towards it, received one end of the sash-bar, while the other rested in an inclined position against a wooden rail (b) placed longitudinally above the pulleys, having as many sinkings thereon as there were drills. The traversing-plate being then pushed forward, the sash-bar was perforated by the drill; the plate was then drawn back, and the same operation repeated with the other end of the bar, which left it ready for fixing.

The action of the traversing-plate (c) is shown more distinctly in the second engraving.^[7] One out of every nine of the sash-bars of the roof is stronger than the rest, to serve for fixing the ridge previous to glazing. These extra-strong bars are two inches wide and one inch and a half deep, and were formed by the same machinery already described, by an adjustment of the different cutters and saws.

THE total length of these required was about sixteen miles. They are cut out of timber three inches square, in section, and are of the form shown in the diagram, with a groove on each side to receive the glass. This was also done by machinery which, with about five-horse power, turned out one hundred lengths of twenty-four feet in a day of ten hours, allowing the time for the necessary stoppages. After they had been delivered at the building, these ridge-pieces were cut to the exact lengths by means of the same apparatus used for the solid gutters which has already been described. At each end of the ridge-piece two holes were also drilled to receive dowells to connect it with the adjoining length. By no other than mechanical means could the immense number of holes thus drilled have been placed so exactly that those in the opposite ends of any two ridge-pieces should correspond precisely.

The different essential component parts of the roof having thus been described, we propose to take the different members of the construction in succession downwards.

BUT first it may be mentioned here that the glass used throughout the building is sheet, on an average about one-sixteenth of an inch thick, and weighing one pound per foot superficial. This gives an aggregate weight of about four hundred tons for the whole of the work, the greater part of which was supplied by Messrs. Chance and Co., of Birmingham. Each square is forty-nine inches long and ten wide, the greatest length of sheet glass that has ever been made in this country. The manufacture of this kind of glass is of comparatively recent introduction into England, though practised for some time on the Continent; and the rapid progress made by the manufacturers alluded to must be in a great measure attributed to the wise removal of the fiscal burden on the article, made by the late Sir Robert Peel. That lamented statesman, with his usual foresight, doubtless contemplated that great social benefits would follow from that enactment; and it is, perhaps, not too much to say that, but for Sir Robert's enlightened measure, this "huge pile of transparency" would never have been reared.

IT has been mentioned that the triple gutters deliver the water into main gutters running in the transverse direction of the building; these are formed of wood, with a bottom piece, into which are grooved two upright sides, they are firmly bolted down upon the upper flange of the roof-girders, and where these are quite horizontal the fall in the gutter is given by a false bottom laid to a slope. Of these gutters there is a length of about five-and-a-half miles in the building, which, added to the aggregate length of the Paxton's gutters, makes a total of about twenty-five-and-a-half miles of gutter.

THESE are of cast-iron, where not more than twenty-four feet long, and the rest of wrought-iron. The cast-iron ones are precisely the same in appearance as those used for the galleries, but lighter in metal; a separate description of them is not, therefore, necessary. The weight of each of these girders is twelve cwt., and each was proved to nine tons previously to being used; but it is calculated that the greatest weight they may have to bear will not exceed five tons: the total number required was about 470.

The wrought-iron girders, or trusses, are partly forty-eight and partly seventy-two feet long, to span the avenues of those respective widths; the principle of the construction is the same in each. The top rail (if it may be so called) of the truss is formed with two pieces of L section iron placed back to back double L sections, and the bottom rail with two flat bars parallel flat bars, the total depth being three feet; at the ends these bars are riveted on to cast-iron standards, and the intermediate distance is divided into eight-feet lengths by other cast-iron standards, to which the bars are also riveted, and thus a framework of rectangles is formed. In the trusses forty-eight feet span there are, therefore, six such divisions in the length, and nine in those of seventy-two feet span. These are then divided in the direction of ONE of the diagonals by a flat bar passing between and riveted to those forming the top and bottom rails. This completes the constructional part of the truss; but to render the appearance more uniform with that of the cast-iron girders, a flat bar of wood (shown by the dotted lines) is made to form the other diagonal of the rectangles.

The trusses for a span of seventy-two feet are cambered or bent upwards about ten inches, which both adds to their strength and improves the appearance. The form and arrangement of these roof-trusses may be clearly traced in several of the views of the interior which are presented to the reader. The weight, when completed, of each of the trusses of seventy-two feet span is about thirty-five cwt., and of those of forty-eight feet span about thirteen cwt.

It has been already mentioned that four of the roof-trusses vary from the rest on account of the greater load they have to sustain. The depth of these exceptional trusses is six feet, and their length seventy-two feet, or the width of the main avenue, which they bridge over. The principle of their construction is similar to that employed in the lighter trusses; but the arrangement of the parts is somewhat modified. The top rail consists of two pieces of L section iron, placed, as before, back to back; but they are further connected on the top by a flat piece double L sections with flat. The lower rail is formed by two flat bars placed upright parallel flat bars, and these are riveted at the ends to standards of cast-iron, which, however, are considerably heavier in construction than those before described; and they have also in the centre, at (a) two slots, or sinkings, into which the ends of two of the diagonal bars are riveted. The whole length is then divided into three equal parts, each 24 feet long, by strong CAST-iron standards at (b) the ends of which are riveted between the rails, and these spaces are again subdivided into three eight-feet lengths by WROUGHT-iron standards at (c c). The top of each standard is next connected with the foot of the next but one to it by diagonal flat bars, which, together with the short pieces fastened into the slots at (a), complete the figure of the whole, forming a kind of trellis-work, two diamonds in depth. In the diagram only half the length of the girder is shown.

The dimensions of the different bars of iron in this piece of construction are proportional to the amount of strain they have to bear. The two heavier out of the four trusses just described weighed when completed eight tons each, and the other two, which are of rather lighter construction, six tons each.

The riveting together of the wrought-iron trusses was performed on horizontal supports, on which the curve that they were to be made to was marked out. The bars having been previously cut to the requisite lengths, and punched and drilled with holes for the rivets, were laid out on the stages in the proper forms with the cast-iron standards, which were temporarily kept in place by bolts passed through some of the rivet-holes. The whole framework was then riveted up with red-hot rivets supplied from small portable furnaces, several sets of men being employed upon each truss, by which means as many as sixteen were completed in one day. The whole of the trusses, three hundred and seventy-two in number, required for the building were put together on the ground, and several ingenious mechanical contrivances were made use of to facilitate and hasten the work. To form some idea of the amount of labour that had to be performed, it may be mentioned that each of the trusses forty-eight feet in length, or the smallest, is held together by more than fifty rivets, requiring more than twice that number of holes to be made in bars of iron varying in thickness from a quarter of an inch upwards. About 25,000 rivets were thus required for the whole of the work.

THE holes for the rivets were made partly by drilling and partly by punching. In the machine used for the former the bar to be bored was laid upon a flat surface forming part of the solid cast-iron stand of the machinery; the drilling-point worked vertically, and could be moved in that direction to suit the different thicknesses of iron brought under its operation. It was suspended at one end of a lever, with a counterpoise at the other. This lever was also connected by a rod and crank, with another near the ground, one end of which was formed into a tread to be worked by the foot. The workman, when he had arranged the iron in the right position under the drill, pressed his foot upon the tread; thus raising the counterpoise end of the upper lever, and pressing the point of the drill, which was of a spear-head form, down upon the iron. Underneath the iron to be drilled was placed a piece of wood to protect the point of the drill when it had passed through the iron. It was also necessary to moisten the iron during the operation, in order to keep the drill-point cool. Three men were required to attend to this work, which was not so rapid as the other method of making the holes by punching.

THE enormous power exerted by this piece of machinery renders it necessary that the stand containing the punch, &c., should be exceedingly solid, and it is formed accordingly by a heavy mass of cast-iron, in which there are two indentations, as seen by the engraving. In the lower of these the punching operation is performed, and in the upper there are shears for cutting off the ends of the bars when required. The motion is communicated to each of these by means of a cogged wheel at the back; but both the punch and the shears work in a vertical direction, slowly moving up and down with irresistible force. There is no sudden blow or jerk, which makes the effect the more striking, as the unpractised eye has no means of discovering the amount of the force which is being put in operation. It is, however, so great that, although the punching of a hole scarcely occupies two or three seconds, the iron becomes quite hot from the effect of the pressure. In using this machine, the workman arranges the iron bar on a solid rest, placing it so that when the punch descends it makes the hole in the position required. As soon as the punch has passed through the bar, the action of the machinery is reversed, and the instrument ascends again; during which time the bar is re-arranged, and the operation is thus continually repeated. This piece of machinery also requires three men to work it, if the bars to be punched are of considerable length, so as to require the ends to be held up; otherwise, one alone is sufficient; and in the course of a ten-hours day about three thousand holes can be punched out—the number, of course, varying according to the thickness of the bars.

Neither of the mechanical contrivances just described are novel inventions, though they are thus, perhaps, brought for the first time under the notice of many of our readers, to whom they may be so far rendered interesting from their being connected with the execution of THE building of the day.

AT the Chelsea Saw-mills, where the reader has already seen the Paxton's gutters shaped out, another interesting piece of machinery was in use for these works, for the purpose of finishing planks to a certain size and thickness, called the adzing and planing machine. An adze is a tool used by carpenters to remove any unevenness in the surface of a board in a particular spot. In this piece of machinery two cutters are fixed to a revolving arm, under which the plank is made to pass; and as it does so the cutters remove a certain thickness from the whole of the surface. The arrangement of these cutters is very plainly shown in the annexed engraving. On the under-side of the same bench to which this apparatus is fixed, three planes are set, each at an angle of about 5 degrees, by which the under-side of the plank is brought to an even face, while the upper surface is operated on by the adzing-cutters, and in this manner the plank is reduced to an even thickness throughout. As it passes on it is brought between two circular saws, which are adjusted to the width which it is desired to give to the plank. It is dragged forward towards the planes and cutters by means of an endless chain, composed of open links; which chain passes over a wheel provided with projecting pegs, so arranged as to fit into the links. The plank is kept down upon the planes, and otherwise held in position, by pressure-rollers.

THE columns in the building perform three important offices. They support the roof and the galleries, and serve as pipes to convey the rain-water from the roofs. Their form, which is beautiful, both mechanically and artistically, was suggested by Mr. Barry; it is a ring, eight inches in diameter externally, the thickness varying in the different columns, according to the weights they have to support respectively. Four flat faces, about three inches wide, are added on the outside of this ring, so that when the column is in its place, they face nearly north, south, east, and west. The column may therefore be considered as a hollow tube, of the section just described, and of the same form at each end, having at its extremities horizontally projecting rings called SNUGS, through which the bolts are passed, to fasten the columns to the connecting-pieces and base-pieces. That the hollow form adopted for the columns is that best suited to obtain the greatest strength with the least amount of material has been abundantly shown by experiments, as even two straws placed in an upright position will bear a very considerable weight; it is that also seen in the structure of the bones of animals. Of these columns there are 3,300 in the whole building.

Those portions of the height of the columns which correspond with the depth and position of the girders form separate lengths, which are called connecting-pieces, as they unite the lengths of columns of the different storeys. These connecting-pieces have the same sectional form as the columns themselves, and, like them, are the same at each end, where there are projections cast on, which serve to support the girders, and which are provided with holes through which the bolts pass to connect them with the columns. These holes alternate with the projections to receive the girders, which projections are so formed that they clip others cast on to the ends of the girders, which will be hereafter described. In the centre of each projection there is formed a small notch which receives the key or wedge for fixing the girders.

The meeting faces of the columns and connecting-pieces were all turned in a lathe, in order that, when set up, they might fit so precisely as not to require any packing to adjust them in an upright position; and only in the cases of those columns which serve as water-pipes is any such packing introduced. In those a piece of canvass, with white lead, is put into the joint. An enormous amount of additional labour was involved by this proceeding, as no less than twelve hundred of such faces had to be operated on; but this did not deter the enterprising contractors, who were fully alive to the importance of the object to be attained. When fixed, the projecting "snugs," with the bolts passing through them, were covered by ornamental caps and bases of cast-iron, fixed after the rest of the work was completed.

THE lower storey of columns in every case stands upon base-pieces of which the upright portion is a continuation of the column, with "snugs" at the top, to correspond with those of the column, and standing on a horizontal bed-plate, from which "shoulders" rise to strengthen the upright portion. These bed-plates vary in size from three feet by two feet to one foot six inches by one foot, in proportion to the weight which the several superincumbent columns have to sustain. The longest dimension of the bed-plate is in the transverse direction of the building, in which the greatest overturning strain might be expected to act upon the columns. From the vertical portion of the base-pieces, sockets six inches in diameter project, in the direction of the length of the building, into which are fitted the cast-iron drain-pipes, which convey away the water brought down by the columns from the roof. The height of the base-pieces varies to suit the different levels at which the floor is supported above the ground. These levels had therefore to be determined in every individual instance previous to the castings being made. It was done, however, with such precision that, when they came to be used, they were all found to be of the exact length required for their situation. Of these base-pieces, 1,074 were required for the building.

IT has been mentioned that the columns supported girders at three different heights, dividing the greatest altitude of the building into three storeys; and that the lower tier of girders, where the building consisted of more than one storey, served to support a gallery.

These gallery girders are all twenty-four feet long and three feet deep, the upper and lower "flanges" or rails having a T section formed section with standards at the ends of similar section. The rectangular space between them is then divided into three equal parts, by uprights having a + section form of section, and the three smaller spaces thus obtained have diagonal "struts" in each direction. The girder thus described forms a double truss, in which the diagonal braces are subjected both to the strain of compression and tension. At the top and bottom of the end-standards small projections are cast on, by which the connecting-pieces hold the girders; and at each end of the flat portion of the top and bottom rails small sinkings are cast, by means of which the girder is keyed up to its position. The flat portion of the upper and lower "flanges" of the girder is swelled out in width from the ends towards the centre, in order to increase the quantity of metal in that part where the strain is greatest.

The description just given of the gallery girders will apply to all the cast-iron girders throughout the building, of which there are 2,150; the only difference between them being, that those for the roofs or other internal portions, where no gallery is to be supported, are cast with a less amount of metal. The form of girder just described, which is unusual, was the result of several experiments performed under the superintendence of Messrs. W. Cubitt, C. H. Wild, C. Fox, and other gentlemen, previous to the commencement of the building; and the thickness of metal for the different parts of these, as well as for all the other cast-iron work in the building, was minutely calculated and determined by Mr. C. H. Wild and Mr. C. Fox, under the supervision of Mr. Cubitt, the President of the Institution of Civil Engineers, to whom the Royal Commission had intrusted the responsible duty of the chief superintendence of the whole of the work.