The Crystal Palace

by Peter Berlyn; Jr. Charles Fowler

A PAIR OF RIBS PREPARED FOR RAISING.

"The whole framework was then moved on rollers to the centre of the square formed by the intersection of the transept and the main avenue, where it was afterwards hoisted. All the ribs were landed over this square, and were afterwards moved on a tramway formed of a half baulk of timber constructed over the columns on either side of the transept, at a height of about four feet above the lead-flat. The hoisting-tackle consisted of four crabs, each one being placed on the side of the transept opposite to the part of the ribs to be lifted by it, so that the men at the crabs might watch the effect of their exertions with greater convenience."

"The hoisting-shears were placed on the lead-flat immediately over the deep trusses of seventy-two feet span; each set consisted of three stout scaffold-poles, lashed together at the top, and footed on planks laid across the flat, and secured by the necessary guy-ropes. The hoisting-rope passed from each of the crabs across the transept horizontally, to a leading block attached to the foot of the opposite angle column of the square; it then passed up to a treble block fastened to the shears on the flat, and from thence down to a double block secured by chains to the bottom part of the ribs."

Hoisting the Ribs for the Transept Roof.

"There was a peculiar difficulty to be overcome in this operation, which arose from the circumstance that the width of the framework was greater than that of the transept, the extreme width of the framework to be hoisted being seventy-four feet, and the clear width apart of the trusses above which it had to be hoisted being only seventy-one feet four inches. It was therefore necessary to raise one side to a height of thirty-five feet before raising the other, so as to diminish the horizontal width of the whole, the diameter of the semicircle being maintained at this angle; the whole was then hoisted, until the highest end could clear the tramway."

This accounts for the slanting position in which the ribs are shown in the view given.

"The foot of the ribs on one side was then passed over the tramway sufficiently to allow the other side to clear the opposite truss; after which the whole was hoisted to the full height, and rested on rollers of hard wood placed between the sills attached to the framework and the tramway, by means of which it was moved to its permanent position. There it was again raised by another set of shears, while the sill and tramway were removed from under it; and the ribs were then lowered into the sockets prepared for them, formed by the continuation of the columns above the level of the lead-flat."

"Each successive pair of ribs was fixed at a distance of twenty-four feet, or one bay from the preceding one; and the purlins, &c., were fixed in the intervening space without any scaffolding from the ground, by means of jointed ladders, which were adjusted to the form of the roof."