THE RAISING OF THE DRY-DOCK DEWEY. 141 
the high side when that side had been raised out of the water, and the out- 
side head lessened. Consequently it was abandoned. 
It was then attempted to operate the dock’s forward centrifugal pump 
under water by means of compressed air, the exhaust pipe having been run 
above the water-line from the outboard connection through the side wall. 
The pump was started by this means, but only 30 pounds pressure could be 
obtained with the air plant available, and this was not sufficient to eject 
any water against the outside head. In fact a minimum of 80 pounds press- 
ure is required under normal conditions to operate this pump. This method 
was also abandoned. Subsequent events showed that it would have been 
impracticable even had sufficient air capacity been available. 
The second method of attempting to raise the dock by steam on its 
own pump wasthen takenup. After many annoying difficulties, the pump 
compartment bulkheads were finally made water-tight, the bulkheads 
sufficiently strengthened and the compartment cleared of all but about 2 feet 
ofwater. About 3 P. M. on June 14, 1910, the dock’s own pumpwas gotten 
in operation by steam from the Wompatuck. ‘The discharge had already 
been cleared by divers digging away the 14 feet of mud and hard sand in 
which it had sunk. 
Fig. 2, Plate 72, shows the first result of operating the dock’s own pump. 
The starboard side came up first, the pump taking water from the tanks in 
that side before it would take any water whatever from the tanks in the 
low side. The vent pipes from the tanks in the low side had been fitted with 
hose connections to the atmosphere and there was no indication of any air 
going into them, which would have been the case had the pump been taking 
water from them. This was due chiefly to the fact that all compartment 
valves are of the quick-opening type, many being operated by one lever, 
which prevents them from being anything but approximately tight. The 
leakage was, however, far greater than had been anticipated. Furthermore, 
these valves occasionally break in use and no doubt some were broken. 
Also some of the drainage piping was leaky through small holes in it and this 
also allowed water to pass from some of the compartments to others. No 
matter which valves were open or closed, the pump took water from the 
high tanks before removing any from the low tanks. This action was wholly 
unlooked for. This operation was then stopped temporarily. The No. 1 
tanks on the high side were then completey filled with water and the vents 
plugged. At about 9.30 P. M. the dock’s pump was again started with the 
same result as before. The starboard side came up first,and at about 5 A. M. 
the next morning it had been raised to about 14 feet on the draft board at the 
forward end, and 24 feet on the draft board at the after end. (These drafts 
