is 68 feet. At the point of intersection of the nave with the end transepts, the roof is flat, and forms a parallelogram of 72 feet square. On each side of the nave are aisles of 24 feet in width, formed by the columns which support a portion of the building. Beyond these first aisles, and parallel with them at a distance of 48 feet, are second aisles, 43 feet in height, and again beyond these, and at the same distance, are third aisles of the same width and height. At alternate distances of 72 feet and 24 feet, columns project 8 feet into the nave, which, continued up nearly to the roof, support an upper gallery, which runs completely round the building, and sustain also the arched girders which carry the semi-circular roof of the nave. A gallery, 24 feet in width, runs entirely round the building on the sides nearest the exterior, and round four courts, 48 by 120 feet, which abut on the central transept. This lower gallery is reached by eight double staircases, four being placed at each portion of the building, divided by the central transept. From the first or lower gallery, access is obtained to the upper 8 feet gallery by eight spiral staircases, one being placed at each end of the three transepts, and one at each end of the building. The second tier of columns supports in the transepts only a platform, or landing place, 24 feet in width, and 72 feet in length, with the exception of the larger one in the centre, the length of which is 120 feet, and from these platforms, at an elevation of 42 feet from the ground, a continuation of the spiral staircase leads to the second or upper gallery, at a height of 62 feet. The passage along this gallery is through a series of ring or "bull's eye" girders, 7 feet in diameter, resting upon the columns which project into the nave, at alternate distances of 24 and 72 feet. The views from this gallery, whether of the busy scene far down below into the nave of the building, or through the glazed windows over the surrounding country, or of the gradual diminution of the size of the hoops of the girders as they fade away in the long perspective of the gallery, will amply repay the visitor for the trouble of ascending. In the central transept there is yet a third gallery of 8 feet in width, which runs completely round the transept, crossing the nave at an elevation of 100 feet, and on a level with the top of the arched roof of the nave. The ascent to this third or uppermost gallery, is made from spiral staircases ascending from platforms at each end of the large transept. The view of the park and grounds, and of the surrounding country, from this elevation will repay the visitor for the trouble of ascending.

The ribs which support the semicircular roof of the nave and two end transepts are of wrought iron. At alternate distances of 24 and 72 feet are semicircular lattice-work girders, eight feet deep, which rest upon, and spring from the upper surface of the "bull's eye" girders just mentioned. These girders are connected and made rigid by other longitudinal girders of six feet in depth between the shorter spaces, and of three feet in depth between the longer intervals. The whole of the arch of the roof is divided into seven

equal parts by these longitudinal girders. The visitor, while he is struck with the imposing grandeur of this noble vaulted roof, will not fail to notice that it lacks that soft aërial perspective and atmospheric tint, which proved so prominent and marked a feature in the flat roof of the late Exhibition Building in Hyde Park. The necessity for greater depth, and more frequent intersection of the girders, has rendered this change unavoidable, but the vastly improved character of the edifice, by the substitution of an arched for a flat roof, more than compensates for the absence of this feature of the former building. The central portion of the roof, which rises eight feet above the upper surface of the girders, is fitted on each side with louvre plates for the purpose of ventilation. The girders which support the roof of the great transept are deeper and stronger than those of the smaller ones. The construction of this roof-one of the proudest monuments of engineering skill in the country-was the heaviest portion of the work connected with the erection of the Crystal Palace; and the melancholy accident of the falling of the scaffolding retarded its completion for more than three months. The scaffolding was originally constructed upon the suspension principle, the ends resting upon the upper tiers of girders. As many of the bridges of the present day, even upon railways, are constructed upon the same system, and have stood the test of long experience, there can be no doubt as to the safety of the principle applied, and the accident could only be ascribed to some imperfection or flaw in the materials employed. In order, however, to prevent any possible chance of the recurrence of such a disaster, the contractors proceeded to erect a new scaffolding from the ground, and which, when completed, was one of the most remarkable works of its kind probably ever constructed. Upwards of 22,000 cubic feet of timber, and fifty tons of iron, were employed in it. Three rows of timbers of a foot square, and 24 feet apart, were raised on end along the centre of the transept, and retained in their position by "binders" of deals 3 inches by 12, and diagonal bars of iron bolted to the timbers. At a height of 21 feet, pieces of timber, five inches square, rested longitudinally on the upright pieces, and were further strengthened by diagonal supports, stout struts," and iron bars, which prevented the slightest movement in any direction. Each story of the scaffold was constructed in a similar manner until far aloft, at the dizzy height of nearly 200 feet, it supported a substantial stage, upon which a battalion of guards might have bivouacked with safety and comfort, or a monster band might have enlivened a crowded promenade concert, or a monster bal-masqué. With towering ambition we once soared to this giddy height and looked down, not with scorn, but with fear and trembling, on the dwarfish world below us. Our guide and several of the workmen jumped upon the loosely nailed boards to convince us there was no vibration, but we felt, we confess, a slight tremulous motion; it was not, however, in the

scaffolding, and self-respect forbids our stating the precise locality where that peculiar sensation was experienced. We assured our guide we were satisfied, that it was unnecessary, in order to convince us, to repeat the experiment. After the very intelligent foreman, Mr. Wilbee, had pointed out to us the spot from which the previous scaffolding fell, we descended a very lofty and perpendicular ladder, which had not the advantage of Jacob's ladder of" one end resting upon the earth," for it stood upon one or two isolated planks, a slip of the foot from which would soon have landed us upon terra firma. Finally, in our descent we reached one of the upper galleries, and as we flattered ourselves that we had performed as great a feat as the ascent of Mont Blanc, we received from our guide the alarmingly complimentary assurance that there were not ten men in a hundred of the workmen employed in the building who would have ventured where we had dared; and we thought that, slightly altered,

"Fools rush in where angels fear to tread,"

might be considered by some persons as a line not altogether inapplicable to ourselves.

The Palace, exclusive of the wings, is supported on the ground floor by 968 columns, secured in their position by a nearly equal number of cast and wrought iron girders; the former building in Hyde Park rested upon 1,060 columns, or 92 more than the present edifice. The second tier of the building is formed of 898 columns, and the third of 340 columns. The entire length of the building is occupied by 68 columns, placed 24 feet apart, and, at intervals of eight feet between these columns, are placed half columns of wood of the same form and appearance as the iron columns, and being 136 in number on each side of the building. The greatest number of columns in the direction of the breadth of the building is 17, and there are six rows of these near the central transepts. In every part of the building the columns are placed either at distances of 24 feet apart or multiples of that number. The columns which project into the nave are 8 feet, or one third of 24 feet; in the larger courts, they are so placed as to form courts of 48 by 72; the nave and end transepts are colonnades of 72 and 120 feet, and the wings of the building range between 32, 48, and 96 feet. The wings are each 576 feet in length. At the points of connection with the main building, the wings are 96 by 24 feet; they then assume the dimensions of 72 by 48 feet. Next, a long avenue of 384 feet in length (the same as the great transept) by 32 feet in width. Each wing terminates in a cross of 96 by 48 feet at the centre of intersection; and on the suminit of the wings are watertanks 48 feet square, capable of containing 800 tons of water. In the highest portion of the wings there are three stories, and in one of these at each wing are placed the refreshment-rooms.

The iron columns which support the building are hollow, and are 8 inches in diameter, the thickness of the metal varying, according

to the weight which each has to carry, from three-eighths to nineeighths of an inch. The columns present the appearance of flat bands placed upon the ordinary circular form, and from their form are admirably adapted for the connection and attachment of the girders, which serve at the same time for support for the galleries and roofs, and for giving rigidity to the various parts of the building. Each of the columns is cast with small projecting pieces of metal, by means of which, short vertical "connecting pieces" may be readily secured to them. These "connecting pieces” are three feet in length, and each are armed on their upper and lower portions with "snugs" or hooks, which "clutching" similiar projections cast on the girders, effectually secure them in all directions. The girders, with the exception of those referred to as supporting the semicircular roof, are formed some of cast, and others of wrought iron, and are all three feet in depth. The galleries of the different tiers rest upon these girders, and where there are no galleries, the girders are still used for the purpose of giving stiffness and rigidity to the columns. The girders are 24 feet in length, and are divided into three parallelograms of 8 feet each, by vertical struts connected at the top and bottom by diagonal tiers; they have been all tested by hydraulic press, to a strain of 15 tons, and their breaking weight is not less than 30 tons; one which was tested with 30 tons, flew so completely to pieces that it was impossible to ascertain with certainty the point at which fracture commenced.

The roof of the building, except in the case of the nave and transepts, is in its general form flat, but is made up of a series of ridges and furrows, which form the peculiar feature of its construction. It is in fact, a network of gutters, beautifully arranged for carrying off the water, and at the same time, serving to support the roof. The rain-water which falls is conveyed away down hollow columns connected with pipes at their base. At every 24 feet are placed transverse zine gutters resting on the upper edge of the girders, and communicating with the columns down which the water is to be conveyed. At intervals of 8 feet, and with their ends resting upon the transverse gutters, running longitudinally, are the famous "Paxton gutters," which convey away simultaneously the rain-water falling on the roof, and the condensed vapour formed inside the building. Of these gutters, a total length of nearly thirty miles has been used in the entire building. Each of these gutters is formed of a piece of timber 5 inches by 6, and 24 feet in length, and it has on its upper surface a semicircular groove of about 1 inch radius, and two smaller grooves downwards at an oblique angle to its sides; the larger grooves convey the water from the roof, and the smaller ones, the condensed water from the inside to the transverse gutters. In order to provide a sufficient fall for the water, each of the “Paxton gutters" is curved or "cambered" in its under side by means of iron rods to the extent of 2 inches. At each end of the gutter, a

semicircular cut is given through its depth, so that when two of these pieces are brought end to end, the water flows down through a circular cavity into the box gutter, and thence down the hollow columns. An extract from an able paper read by Mr. M. Digby Wyatt, at the Institution of Civil Engineers, will explain the mode in which the roof was constructed. "On each side of the Paxton gutters there are 27 notches, three of which are larger than the others, and on these, bars of wood 2 inches by 11 inch, grooved for glass on both sides, are 'notched' down; these bars form principal rafters; and being set at a pitch of two and a half to one, are fixed to a ridge 3 inches by 3 inches, also grooved for glass on both sides. The long edge of a sheet of glass, 4 feet 1 inch by 10 inches, is then inserted into the groove of the principal rafter, and a sash bar is then brought down and secured to the ridge, and to the edge of the gutter, the lower edge of the glass bedding on putty about inch wide; a little force applied at the lower end, brings the upper edge of the glass home into the groove in the ridge. The glass being then pressed down, the putty is made good in the grooves externally, and thus simply is this system of roofing put together. Its lightness is one of its remarkable qualities, since the entire weight of one superficial foot averages only 3 lbs."

The means of ventilation is produced by a series of louvre plates of zinc, fitting into frames; and which may be opened or shut in a manner similiar to the ordinary Venetian blinds. Small iron brackets are attached to the centre of each blade, and are furnished with eyes, through which are inserted pins passing also through holes bored at equal distances from one another in a kind of rack, so that by drawing these racks up or down, an opening or closing of the ventilators is effected. A large number of these racks are attached to levers, and by means of a series of rods and cranks, a very large space may be opened or closed simultaneously.

Under the ground floor of the building, is what is termed the Paxton tunnel. In consequence of the sloping nature of the ground on which the building stands, having a fall of 26 feet towards the Park front, it was necessary to run up brick piers to support the base plates on which the column rested; and a basement story looking out on to the terrace has been formed where the machinery in motion is exhibited. The tunnel extends from end to end of the building, and it also contains the boilers and apparatus for heating the building; not less than fifty miles of large iron pipes being employed for this purpose. A tramroad traverses the whole length of the tunnel, upon which the fuel for the smoke-consuming furnaces is conveyed. The roof of the basement floor is formed of brick arches, resting on the flanges of castiron girders, supported at one end by a row of monotonous looking iron columns; and upon the other, by a brick retaining wall. The position occupied by exhibitors of machinery is the part immediately facing the grounds.