ANY of the persons who visited the building during the progress of its erection were heard to inquire "where was the scaffolding;" and others even imagined that the skeleton framework they saw was, in fact, only the scaffolding for the building, and not parts of its actual construction. This leads us to point out one of the most interesting peculiarities of the structure; namely, that it formed, as it were, the scaffolding for its own erection. In order to raise the columns upon the base-pieces, two poles were placed upright, connected by a horizontal piece, forming what is called shear-legs; the whole being steadied in its position by ropes from the summit fixed to the ground in various directions. A rope with pulleys fixed to the horizontal piece served to hoist the column, and sustain it in a vertical position until the bolts were passed through the projecting rings at the bottom of the column and the corresponding ones at the top of the base-piece, and screwed up. When two columns had been thus fixed, a connecting-piece was attached to each end of a girder, and the whole raised by the same apparatus, and fixed on the top of the columns; bolts being passed through the holes in the projections of the connecting-pieces, corresponding with those on the top of the columns. The shear-legs were then moved on twenty-four feet to perform the same duties to another pair of columns; and two sides of a 24-feet bay were thus formed. To complete the square, two more girders were raised in a similar manner, and fixed between the connecting-pieces over the columns. The square bay then became a firm structure, requiring no further support; and by repeating these operations all the smaller avenues of the building were erected, of the different heights of one, two, or three storeys. The greatest number of columns thus fixed in one week was 310.
FIXING THE GIRDERS.
General View of the Works in Progress.
HE wrought-iron roof-trusses over the 48-feet avenues were raised in a similar manner to the columns and girders; and in all cases horses were employed to run out the end of the fall-rope, which was passed through a pulley or catch-block at the foot of the shear-legs, in order to change its direction from vertical to horizontal.