Those portions of the height of the columns which correspond with the depth and position of the girders form separate lengths, which are called connecting-pieces, as they unite the lengths of columns of the different storeys. These connecting-pieces have the same sectional form as the columns themselves, and, like them, are the same at each end, where there are projections cast on, which serve to support the girders, and which are provided with holes through which the bolts pass to connect them with the columns. These holes alternate with the projections to receive the girders, which projections are so formed that they clip others cast on to the ends of the girders, which will be hereafter described. In the centre of each projection there is formed a small notch which receives the key or wedge for fixing the girders.
The meeting faces of the columns and connecting-pieces were all turned in a lathe, in order that, when set up, they might fit so precisely as not to require any packing to adjust them in an upright position; and only in the cases of those columns which serve as water-pipes is any such packing introduced. In those a piece of canvass, with white lead, is put into the joint. An enormous amount of additional labour was involved by this proceeding, as no less than twelve hundred of such faces had to be operated on; but this did not deter the enterprising contractors, who were fully alive to the importance of the object to be attained. When fixed, the projecting "snugs," with the bolts passing through them, were covered by ornamental caps and bases of cast-iron, fixed after the rest of the work was completed.
HE lower storey of columns in every case stands upon base-pieces of which the upright portion is a continuation of the column, with "snugs" at the top, to correspond with those of the column, and standing on a horizontal bed-plate, from which "shoulders" rise to strengthen the upright portion. These bed-plates vary in size from three feet by two feet to one foot six inches by one foot, in proportion to the weight which the several superincumbent columns have to sustain. The longest dimension of the bed-plate is in the transverse direction of the building, in which the greatest overturning strain might be expected to act upon the columns. From the vertical portion of the base-pieces, sockets six inches in diameter project, in the direction of the length of the building, into which are fitted the cast-iron drain-pipes, which convey away the water brought down by the columns from the roof. The height of the base-pieces varies to suit the different levels at which the floor is supported above the ground. These levels had therefore to be determined in every individual instance previous to the castings being made. It was done, however, with such precision that, when they came to be used, they were all found to be of the exact length required for their situation. Of these base-pieces, 1,074 were required for the building.
BASE-PIECE.
T has been mentioned that the columns supported girders at three different heights, dividing the greatest altitude of the building into three storeys; and that the lower tier of girders, where the building consisted of more than one storey, served to support a gallery.