874 REPORT—1885. 
of the Forth Bridge have been neither few zor unimportant, it is patent, 
to even the uninitiated, that causes for anxiety will neither disappear nor 
diminish till the erection of the steel superstructure has been completed. 
Presently my remarks will be confined to the main steel piers and 
approach viaducts. The term steel piers refers to those parts of the super- 
structure immediately over and between any of the three groups of four 
caissons. Described generally, each may be said to consist of two sloping 
and two vertical planes ; the sloping, including one connecting horizontal 
column and two 12-foot rising columns, joined at the upper extremi- 
ties by the top member, while from the lower end of each to the top of 
the opposite one there extends a diagonal eight-foot tube. These two 
planes run parallel with the centre line of the bridge, and are 120 feet 
apart at the base and 33 feet at the top. 
The vertical planes complete the structure at the ends of the two: 
sloping planes. They consist of the 12-foot rising columns, already 
mentioned, with the lattice bracing joining these together. These mem- 
bers, with the internal viaduct and the bracing girders attached to the 
skewbacks, form the principal parts of the steel piers, the extreme height 
of which is fully 340 feet above the bottom of the lower bedplates. 
The approach viaducts are, generally speaking, of ordinary design, 
with the exception of some special features to meet the unusual require- 
ments demanded of them. The girders span a distance of 160 feet, and 
rest on granite-faced piers, rising to a height of 130 feet above high 
water; the heights of these piers themselves gradually diminishing as 
they near the abutments, owing to the rising nature of the banks of the 
river. 
The magnitude of the main steel piers, both in respect of their great 
height and immense weight, demands that exceptional means be employed 
in their erection. Many proposals for effecting this have been suggested, 
and may be said to range from that of Mr. Arrol’s first, which was to 
run up the columns independently, using them as the only staging, to 
that proposed by Mr. Baker, viz., to carry up simultaneously with the 
columns a rising platform, extending round the whole four columns, by 
utilising them as supports, and upon this platform to carry up the top- 
member, having the end junctions all previously riveted up, so that on 
arrival at the top the final closing lengths of the 12-foot rising columns. 
had only to be joined to the junctions already fitted, to complete this 
part of the work. After careful consideration the weight requiring to be 
lifted was found to be too great, when compared with the advantages 
to be gained, to allow of its full adoption. In the case of the Fife and 
Queensferry piers, the weight was close on 1,200 tons, and several hundred 
tons more in that of Inch Garvie. 
A modification of this plan is that finally adopted by Mr. Arrol, with 
Sir John Fowler and Mr. Baker’s full approval. The carrying up of the 
top member is done away with, but otherwise it is very similar. 
The main lifting girders of the platform pass through the 12-foot. 
rising columns, and running in line with the vertical planes extend from 
the one sloping plane to the other. Lying across these are placed other 
four girders, one being on either side of each set of 12-foot rising columns, 
thus completing a rectangular platform resting indirectly on the main 
rising columns. The weight of this platform, including the necessary 
cranes and other plant required during the erection of the higher parts of 
the pier, will be about 400 tons. 
