884 REPORT—1885. 
work bases. The last span is over the existing Esplanade, and consists 
of a pair of hog-backed girders of 100 ft. span resting on two brick piers. 
3. The viaduct proper has seventy-four spans of various dimensions, 
consisting of wrought-iron girders resting on piers—Nos. 4 to 78. The 
piers are constructed with a pair of cylinders connected at a short distance 
above high water, and on which is a wrought-iron structure of heights 
varying from 10 ft. to about 70 ft., the top of which carries the girders. 
The cylinders of about two-thirds of the piers—Nos. 5 to 53—are con- 
structed with a wrought-iron caisson lined with brickwork and filled 
with concrete up to low-water level; above this is a brick shaft also filled 
with concrete. Those for the remaining third—Nos. 54 to 77—are of 
cast iron lined for their whole height with brickwork, and filled with 
concrete. The bases of the cylinders are of various diameters—10 ft. for 
the piers of the smallest spans to 23 ft. for those of the largest; and, 
except in the few cases where rock is met with, the cylinders are being 
sunk to depths varying from 20 ft. to 30 ft. below the bed of the river, so 
as to be out of reach of the scouring action of the tide. Before building 
the upper part, the cylinder foundations are tested with a weight 33 per 
cent. greater than the maximum load which can come upon them. At 
14 ft. above high water there is a strong connecting piece between the 
pair of cylinders constructed with cast-iron girders, wrought-iron ties, 
brickwork and concrete; its height is 8 ft., and width nearly equal to that 
of the cylinders. On the top of each cylinder and above the connecting 
piece rises an octagonal shaft of wrought-iron, the base of which is formea 
of a gridiron framework of channel irons attached to the cylinders by 
long wrought-iron bolts. These shafts are joined together near the top 
of the pier by a semicircular arch, forming at the top one structure 
sufficiently wide to carry the girders. The whole of this structure is 
constructed of wrought-iron plates, riveted together with channel, Tee, 
and angle irons. The dimensions of the girders for the seventy-four 
spans are very various, and are as follows :—Eleven spans with 245 ft. 
girders, two spans with 227 ft. girders, one span with 162 ft. girders, 
thirteen spans with 145 ft. girders, twenty-one spans with 129 ft. girders, 
one span with 113 ft. girders, twenty-four spans with 71 ft. girders, and 
one span with 56 ft. girders. The thirteen large spans, with 245 ft. and 
227 ft. girders—between piers 28 and 41—are near the middle, and over 
the navigable channel of the river. At each of these spans there is a 
pair of hog-backed girders, the rails being laid between and at the bottom 
of them. The rest of the spans—twenty-four on the south side, and 
thirty-seven on the north side—are constructed with four rectangular 
girders, the two outer ones being the girders of the old bridge. At 
these spans the rails are laid on top of the girders. The flooring or deck 
plating is corrugated in form, and is constructed, at the large spans, of 
channel irons and plates riveted together, so as to form alternate troughs. 
and ridges; and at the smaller spans of steel plates hydraulically pressed 
into a corrugated shape. 
On each side of the viaduct for its whole length is a wrought-iron 
latticework parapet or wind screen 5 ft. high above the rails. 
The Act of Parliament for the undertaking was obtained in 1881, but 
the contract for the works was not settled until April 1882, owing toa 
question raised with the Board of Trade concerning the ruins and débris 
of the old bridge. The present state of the works is as follows :—The 
arching at Wormit and the Esplanade spans are completed to the level of 
