THE RAISING OF THE DRY-DOCK DEWEY. 143 
The third method of raising the dock, outlined above, and for which 
preparations had been in progress, was then begun. ‘The whole sunken 
side was made water-tight, the bulk of the work being on the top deck 
of the side walls, which had a great many nonwater-tight openings in it. 
Five cofferdams were used as follows: 
The first cofferdam from forward was the one previously fitted for 
obtaining access to the dock’s own forward pump. ‘The 10-inch centrifugal 
pump and the 6-inch pump were retained on this coflerdam for use in pump- 
ing out the whole machinery space after opening up the end bulkheads of 
the pump compartment that had previously been made water-tight. 
The second was a large one about 5 feet 6 inches by 7 feet 6 inches 
and was mounted on the dynamo-room skylight coaming. This cofferdam 
was for the purpose of lowering pumps through it, to be mounted on the 
deck of the machinery space below in order to keep the water down after 
it had been removed and the upper pumps having lost suction, and also 
in order to install pumps (if found necessary) for removing the water from 
the No. 7 compartments. No pumps were mounted on this cofferdam. 
The third cofferdam was mounted on the skylight coaming over the ~ 
dock’s middle centrifugal pump. There was mounted on the outside a 
plunger pump with a 6-inch suction, taken from the Piscataqua. 
The fourth cofferdam was built over the door to the valve house and 
was for providing access to the interior of this house for the operation of 
the valves. All windows and ventilators in this house had to be made 
tight and the house had to be very heavily shored inside. It was built of 
thin plating, non water-tight, and it was necessary to make it water-tight 
for the reason that the deck inside of it could not be made so where the 
valve operating gears passed through it. 
The fifth cofferdam wasmounted on the Septenic coaming over the after 
dock pump and a 12-inch plunger bucket pump was mounted on the outside, 
the suction pipe going down inside the cofferdam. All these cofferdams 
were of steel and were shored from the deck of the dock, with the exception 
of the cofferdam over the valve house door which was of wood. ‘These 
cofferdams are clearly shown on Figs. 1 and 2, Plate 75, and Figs. 1 and 2, 
Plate 76, which show the dock after raising. A great deal of diver’s work | 
was involved in closing all openings in the top of the sunken side. ‘These 
were made water-tight as far as practicable and the pumps mounted on the 
cofferdams were then started. They took the water down about 4 feet 
below the deck in the forward cofferdam after which the head of water 
outside was sufficient to make the leakage too great to be taken care of by 
the pumps. The divers were then sent down to make a complete exami- 
