THE RAISING OF THE DRY-DOCK DEWEY. 139 
clear the compartment of water. In addition to this, aduplex pump with 6 
inches suction was mounted on the outside of the cofferdam with its suction 
running down inside. This was in order to keep the water down in the com- 
partment after it had been taken out by the centrifugal pump. The end bulk- 
heads in this compartment were nonwater-tight and were very inadequately 
stiffened. Extensive shoring was necessary to provide against their collapse 
and considerable work was involved in making them water-tight. 
3. By making the whole top and bottom decks and the side walls of the 
machinery space on the sunken side water-tight; then clearing this whole 
space of water, which would provide nearly 3,000 tons buoyancy (about 
5,500 being necessary to lift the sunken side); and then by utilizing the 
dock’s own pump to raise her or, in case of the failure of this, by mounting 
pumps below and pumping water out of the No. 7 compartments. This 
was the surest method, but also the longest and the most costly. 
The second and third of these methods were based on there being no 
serious damage to the dock’s structure and no large opening to the sea. 
This was conclusively demonstrated to be the fact by opening various other 
compartments into the No. 1 compartments on the starboard side, and then 
observing the action of the water in the No. 1 tanks. The opening of the 
other compartments into the No. 1 compartments was accomplished through 
the dock’s pumping and drainage system, the valves in the valve house 
being operated by divers. This showed general leakage but not enough for 
any large opening to the sea. Furthermore, such examination as could be 
made of the dock by divers did not disclose any open manhole nor damage 
to the dock’s structure. The sea valves and the connections of the drainage 
pipes between the middle and end pontoons were, however, inaccessible by 
divers and could not be examined. 
It was necessary that the raising of the dock is accomplished as soon 
as possible owing to the approaching typhoon season which was due in about 
one month. Therefore preparations for the three methods of raising the 
dock were begun at once and at the same time. For the first method, power 
floats containing air compressors and boilers were fitted up at Cavite and 
sent to Olongapo. There were two floats containing each a compressor of 
from 400 to 500 cubic feet of free air per minute capacity compressed to 
100 pounds, and one other float containing five small torpedo air-compressors 
obtained from the torpedo testing room. Twenty manhole covers were 
manufactured, each containing a 14-inch air connection with cut-off valve 
for introducing compressed air, and a 3-inch pipe running through the man- 
hole and extending down to a depth sufficient to reach within one foot of the 
bottom of the tanks. ‘The latter pipeswere for the ejection of the water and 
