PACIFIC RAILWAY, PRINCE RUPERT, BRITISH COLUMBIA. 223 
As the feature of a sectional dock to be used as a whole or separately 
is somewhat new, it is desired to call attention to the fact that the three 
largest commercial docks in the United States, namely, the 10,000-ton 
floating dry-dock of The Tietjen & Lang Dry-Dock Co., built in 1900, the 
12,000-ton dock of the Morse Dry-Dock Co., built in ‘1902 (both in 
New York Harbor), and the 10,000-ton dock of the Port of Portland, 
Portland, Oregon, are sectional docks in five sections each. All of these 
docks are of timber construction and are giving excellent service. 
PONTOONS. 
As previously stated, the pontoons for this dock are to be twelve in 
number, constructed entirely of timber. By referring to Plate 113, there 
will be seen the design and construction plan of these pontoons. They 
are to be 130 feet by 44 feet by 15 feet deep, with a crown of 3 inches at the 
center, and will have 15 trusses spaced on 3-foot centers. There will be a 
center water-tight bulkhead 12 inches thick and above this bulkhead the 
center will be reinforced for carrying keel blocks. There will be three par- 
tial bulkheads on each side to stiffen the pontoons. All diagonal braces 
are heavily reinforced with anchor stocks. The arch brace is made up of 
planking through-bolted with screw bolts and is intended to take the reverse 
stresses when the dock is floating light. This is a considerable amount 
when it is considered that the wings are superimposed weights carried at 
the extreme ends of the trusses, supported by an evenly distributed pressure 
over the entire bottom. Six by 12-inch deck beams are worked across the 
upper and lower truss members, carrying the 5-inch deck and bottom plank- 
ing parallel to, and reinforcing the truss members for the maximum stress. 
This construction also makes it possible to get in double vertical tie rods 
alongside of bulkheads in such a manner that they may be replaced at 
any time. The whole structure is made water-tight by caulking with white 
pine wedges. 
To protect the exterior from toredo and other marine worms, it is first 
thoroughly graved with tar poisoned with arsenic, then sheathed with two 
layers of hair felt, each thoroughly saturated with tar and arsenic, and then 
with creosoted lumber, also treated with arsenic and thoroughly secured with 
galvanized nails. This treatment, together with the facility for inspection 
afforded by the possibility of detaching and docking any pontoon, has been 
found to give satisfactory protection. 
Each pontoon will require approximately 330,000 board feet of lumber 
or a total, including outrigger or prow on the end pontoons, of 4,000,000 
