"The operation about which most anxiety had been felt was the hoisting of the arched ribs of the transept. These ribs were constructed on the ground horizontally, and when completed with all their bolts, two of them were reared on end, and maintained in a vertical position, at a distance of twenty-four feet from each other, by guy-ropes. As the ribs singly possessed little lateral stiffness, they were framed together in pairs with the purlins, intermediate small ribs and diagonal tie-rods, forming a complete bay of the roof twenty-four feet long; two complete sets of temporary ties were also introduced to provide for the strains incident to the variations in position of the ribs during the hoisting. The feet of the ribs were bolted on to a stout piece of timber, and the lower purlins strutted up from the same." In this state the framework is shown in the engraving. [Illustration: 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." [Illustration: 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.