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the operation of rivetting was gone through. A row of temporary forges was By setting up. constructed by the side of the platforms, and the red-hot rivets taken from them were passed through the holes, and hammered by the workmen into their requisite forms.
While these active preparations for the construction of the roofing were in pro- The rate of deli-
. , .. «. n • r l pi It very of columns,
gress, the daily supplies ot castings ot every description were of the most abundant *>c. nature; no less than 316 girders having been cast and supplied in one week. As fast as the columns came upon the ground, they were taken to their places and immediately fixed. Up to the 20th of September 77 columns had been supplied.
Figs. 31 and 32.
By the week ending the 25th of October, the average number fixed per week amounted to nearly 200, and that rate of supply was continued for several subsequent weeks.
The attention of the contractors was next directed to the formation of the The fo"»««'on of
the transept rib*.
transept ribs. The choicest timber was selected for that purpose, and under the careful superintendance of Mr. Fowler, their form was set out upon a platform erected for the purpose, and the timbers for the first rib laid down. When the rib thus commenced was completed, it was made to serve as a template for the construction of a second; and thus one was fitted upon the others, until the pile had accumulated to four. Three of these having been then laid down in other places, the remainder were constructed upon them in a similar manner.
As the preparations for putting together the main structure advanced, it was The prep** of requisite to form the necessary wooden columns, sashes, matched and beaded joiner.- »ork
Framing together of the transept ribs preparatory Xm rawing.
boarding, louvre frames, &c, for the external enclosures. The vertical sashbars, cut at the Phoenix saw-mills, were delivered by Mr. Birch in large quantities. Sash-frames, also cut at the same mills, were supplied, and these were fitted together by the contractor's carpenters, whose time and labour in forming mortices and tenons was much economised by the employment of the machine before alluded to, patented by Messrs. Furness & Co.
As supplies of the smaller castings necessary to complete the various portions of the structure poured in, the work of erection and putting together proceeded with wonderful rapidity. The progressive increase in the number of hands employed affords a tolerable indication of the increasing intensity of the work : —
1850. In the week ending Sept. 6, 39 men were employed.
Oct. 4, 419 ,,
Nov. 1, 1,476
Dec. 6, 2,260
1851. ,, Jan. 3, 2,112
and from that time, until within a month of the opening of the Exhibition, the average number has rarely fallen below 2,000.
The task of raising to their places the 48 and 72-fcet trusses, was accomplished with great facility in the following manner:—A single mast was maintained in a vertical position by ropes, similar to those described as steadying the shear-legs used for hoisting the girders. From the summit of this mast descended other ropes, with blocks and pulleys, for the purpose of gaining power in lifting. What is called a leading or guide-block, having been attached to the bottom of the mast, a rope passing through it was connected with a yoke drawn by a horse. The mast having been placed close alongside the line in which the roof-trusses had to be fixed, and one end of a rope secured to the truss, the draught of the horse caused the truss to ascend to the necessary height, being steadied in its ascent by other ropes secured to its two ends.
When the truss thus hoisted was fixed in its resting place, the mast was moved along a plank by means of crow-bars, being maintained in a perpendicular position by the alternate slackening and tightening of the cords extending from its head to stakes driven into the ground. Having thus been moved 24 feet, it was ready for the operation of a second hoisting. Two of these great masts, fixed on each side of the transept, were used daily, and in one day as many as seven of the great 72-feet trusses have been raised to their proper position and secured, the apparatus for elevating them having travelled in a vertical position no less than 168 feet
Towards the beginning of December the climax of activity was arrived at, and the most trying operation in the whole construction of the building commenced, namely, the hoisting of the main ribs for the great transept roof. The easiest and at the same time the most secure method of proceeding, with respect to the conduct of this operation, had for some time occupied the attention of the contractors. An ingenious suggestion, made to them by Mr. Wilisee, one of their foremen, was at once adopted, and, with certain modifications, it was promptly carried out.
The floor for the lead flat was already completed, so that an admirable stage was prepared upon which to make the necessary arrangements. The ends of the column into which it was designed to drop the ends of the ribs, rose about four feet above the level of the lead flat, and on the tops of those columns timbers were laid, forming landing stages or tram-ways, to receive the ribs when hoisted. It was of course necessary to raise the ribs sufficiently high above the lead flat to enable their ends to descend upon the tram-ways. To effect this it was determined that two ribs should be placed on end, at a distance of 24 feet from each other, and framed together with purlins and diagonal ties, exactly as they would have to be framed in their finished state. Two complete sets of additional temporary ties were further introduced, to provide for the strain to which the ribs would necessarily be exposed from their altered position in the act of hoisting. The feet of the ribs were securely attached to stout pieces of timber, to afford the means of safely attaching the cords by which they were to be raised. Thus framed together, the ribs were moved on rollers to the centre of the square formed by the intersection of the nave and transept.
On the extra strong trusses which have been described as spanning the nave Provisions for at this point, two pairs of shear-legs were fixed at 24 feet from one another, and secured by ropes connecting them with distant portions of the building. These hoisting shears consisted of two legs on each side of the transept, each leg being formed of three stout scaffold poles lashed together at the top, and footed on planks laid across the lead flat. The heads of these shear-legs inclining slightly forwards, had connected with them blocks and pulleys from which descended ropes, attached to the four ends of the two ribs. The hoisting ropes connected with the sets of pulleys passed down from the shears to leading blocks, attached to the four columns at the angles of the intersection of the nave and transept. From these guide blocks they were led off diagonally to four powerful crabs, so arranged that the gangs of men employed at each were placed opposite the end of the rib acted upon by the crab they worked; and thus the foreman of each gang was enabled so to regulate the exertions of his men as to make them correspond with those of the remaining gangs, and to maintain the two ends on each side in a perfectly horizontal plane.
As the diameter of the semicircular ribs exceeded the width of the transept by n»i»ing. their own thickness, it became necessary, in order that they might pass between the trusses, to commence by raising two of their ends to a considerable height from the ground; and to maintain their diameter at the same angle of inclination until they were hoisted above the columns into which they had to drop. On raising them to a height of about 65 feet from the ground, the highest ends were drawn in a horizontal direction, so as to hang over a portion of the lead flats, and thus room was left to allow the other ends to be lifted to a corresponding height on the opposite side. The ribs were shifted slightly in a horizontal direction until the ends came over the columns, they were then lowered down upon rollers placed upon the tram-ways above mentioned, and by means of these rollers the ribs were moved along to the furthest end of the transept. The place in the centre of the building occupied by the ribs thus hoisted was immediately taken by another pair, which were similarly connected, raised, and moved to within 24 feet of the first pair.
When the whole of the ribs were thus elevated to their places, the spaces when raised, how between them were filled up with the necessary intermediate ribs and connections; and thus the whole roof was framed together complete.
The raising of the main ribs commenced on the 4th of December, and the Time o<*oried in whole sixteen were fixed in one week. It occupied about an hour to raise a pair """"^
of ribs from the ground to the level of the lead flat, but the previous prepara»nd number of tions involved a much longer space of time. Eleven men worked at each crab,
men required. or .-....,.
and about 16 were employed on the lead flat, to guide the ribs in their ascent, and see to the safe condition of the shear-legs and tackle. Considering the anxious nature of this performance, it must be regarded as a most gratifying circumstance, that the whole operation was accomplished without any untoward occurrence.
Gluing the No sooner had the skeleton of the transept-roof been completed, than the work
of glazing commenced. For a considerable portion of the height of the curve, ladders and temporary scaffolds enabled the workmen to proceed with their labours; but in order to complete the upper part an ingenious box was constructed, moving on wheels in the line of the gutters. This box was lowered down from the lead-flat at the summit to any portion of the roof.
Gluing the nave The glazing of the nave roof presented formidable difficulties, from the great extent of work to be got through in so short a space of time. The ingenuity of the contractors was, however, brought to bear upon the subject, and provisions were made by them for the simultaneous glazing of large areas, entirely indepen
ronitmction of dent of variations of weather. 76 machines were constructed, each capable of
machinei; accommodating two glaziers; these machines consisted of a stage of deal about 8 feet square, with an opening in its centre sufficiently large to admit of boxes of glass, and supplies of sash-bars, putty, &c, being hoisted through it. The stage rested on four small wheels, travelling in the Paxton gutters, and spanned a width consisting of one ridge and two sloping sides. In bad weather the workmen were covered by an awning of canvas, stretched over hoops for their protection.
How used. In working, the men sat at the end of the platform next to whatever work had
been last done; from which they pushed the stage backward sufficiently far to allow them to insert a pane of glass, and as soon as that was completed they moved again far enough to allow of the insertion of another. In this manner each stage travelled uninterruptedly from the transept to the east and west ends of the building. The dexterity acquired by the men in working the machines
Quantity of work was very remarkable. By means of them 80 men in one week put in upwards of 18,000 panes of glass, being not less than 62,600 feet superficial. The greatest number of panes inserted by a man in one day was 108, being 367 feet 6 inches of glazing. A somewhat similar machine has been constructed for the purpose of effecting any repairs that may be necessary in the finished roof, with the difference that its wheels travel upon the ridges instead of in the gutters, and that of course there is no aperture for the purpose of hoisting.
Rapid supply of Taking into account the innumerable quantity of small castings requisite, and the extreme rapidity with which they had to be supplied, their quality and cleanness is truly remarkable; and the fact of their having all issued from one foundry, that of the contractors at Smethwick, proves the great facility with which work of that nature can be executed in England.
celerity with Among the later operations connected with the completion of the work, the
ingof the nave most remarkable for the celerity with which it was conducted, was the ornamental
'""'' painting of the nave roof. Iron straps, attached to the trusses, supported a
number of scaffold poles, on which a perfect cloud of boards was laid, and as
many as between 400 and 500 painters, by these means, worked their way, with
extreme rapidity, from one end of the building to the other.
The magnitude of this great building elevated into serious undertakings matters The application which, under ordinary circumstances, are accounted little more than trifles, make the jaliery
Hence machinery was applied to the formation of the entire length ot hand-rail required for the galleries. In fig. 33 is represented a set of cutters (A fig. 33), by exposure to the rapid revolution of which, roughly-shaped strips of mahogany were instantaneously converted into smooth and cleanly rounded hand-rails (B fig. 33). A little sand-paper and French-polish sufficed to bring them to their present excellent condition.
In summing up the description of any great engineering undertaking, it is too lwity of often a painful task to have to record the loss of life so frequently involved. Considering the difficulties of construction, the necessary perils to which the workmen were exposed, and their habitual imprudence, arising, partly, from real indifference to danger, and partly from bravado, it has been a source of congratulation that, in the performance of this contract, but very few accidents have occurred, and those, with two or three exceptions, of a slight nature.
Having now brought to a close our description of the building as it exists, and Conclusion, of the processes by which its existence has been developed, it remains only to reiterate our conviction that the courage, energy, and strength represented by its construction should be regarded by every Englishman with emotions conducive to some yet higher manifestation of national capability; and at the same time to express a hope that the products of British industry (of which the building is but the shrine), may display, in a yet higher degree and in a yet more tangible and varied form, the sources of Commercial Power, so many indications of which it has been our happy privilege to trace in the edifice itself.
M. Digby Wyatt.