138 THE RAISING OF THE DRY-DOCK DEWEY. 
paratively hard sand. The top deck of the side walls on the port side was 
about 6 feet under water at the forward end, and about 16 feet under water 
at the after end. These figures should be increased about 2 feet for high 
tide and decreased 2 feet for low tide. ‘The outer edge of the bottom of the 
port side had sunk into the mud to a depth of about 10 feet at the outer end, 
and kept sinking farther into the mud until it was eventually about 18 feet 
in the mud, before the dock was raised. On first sinking the starboard side 
remained afloat, but it was gradually filling with water. Work was imme- 
diately begun to save the starboard side. All openings in the top deck were 
closed water-tight, and five pumps were mounted below in the machinery 
spaces to pump water from No. 1 tanks up through the manholes. These 
pumps were all small plunger pumps being in size 3 inches to 6 inches suction. 
Steam for these pumps was furnished from the dock’s auxiliary boiler 
located in the starboard machinery space and also from a small tug. 
Fig. 2, Plate 71, shows the position of the dock on May 26, 1910, two days 
after sinking. The starboard side had gone down so that its outer end was 
about 3 feet under water. By this time, however, the pumps had been 
mounted and were in operation and the starboard side was saved from further 
sinking and was raised until it was about 2 feet out of the water at the outer 
end, and 12 feet out at the inner end. These pumps had to be kept going 
day and night during the entire time until the dock was finally raised. There 
was always slow leakage to take care of. 
The alternative plans determined upon for attempting to raise the dock 
were as follows: 
1. By introducing compressed air into bottom tanks Nos. 4, 6, 9, 10, 11 
and 12 on the port side. This seemed at first sight the simplest and quickest 
method of raising the dock. Tank No. 7 was not to be utilized for the reason 
that the top of this tank was formed by the machinery deck which had 
many small openings in it, such as deck drains, steam drains, etc., which 
would have made the retention of air very difficult, and the other tanks had 
more than enough buoyancy to lift the sunken side. 
2. By making water-tight the compartment in which the forward centrif- 
ugal pump for operating the dock was located; then clearing this compart- 
ment of water and operating the dock’s own pump by steam furnished from 
the tug Wompatuck. Before doing this, however, it was decided to attempt 
to run this pump under water by means of compressed air. For clearing 
this compartment of water, a steel cofferdam was built and fitted over the 
skylight coaming and a 10-inch centrifugal pump was mounted on a platform 
on theoutside of the cofferdam anditssuction taken downinto the compartment 
below through a small hatch. This pump had a lift of about 30 feet to entirely 
