SALVAGE EQUIPMENT USED IN RAISING SUBMARINE F-4. 9 
with an adequate power plant, including a dynamo, was used for this purpose. The 
dredge had a 10-inch by 14-inch hoisting engine geared to six drums, any one of 
which could be used independently of the others. The deck leads were so arranged 
that drum lines could be taken over the ends and sides of the craft advantageously. 
From previous experience in attempting to anchor where the submarine lay, 
it was obvious that the dredge could not be moored in the customary manner on ac- 
count of the great depth of water to seaward. The expedient adopted was to use 
the submarine itself as the seaward anchor. This was accomplished by sweeping a 
wire hawser around both the bow and the stern of the vessel. These hawsers were 
taken over the end log of the dredge and were secured to timber heads by chain 
stoppers, or to the drum lines. The inshore mooring for the dredge consisted of 
an anchor with a wire anchor line leading to one of the drums. 
Plain wire hawsers of the sizes mentioned were first used for lifting the sub- 
marine. These hawsers were swept under the vessel by tugs. The ends were 
then temporarily transferred to the dredge. Divers were sent down after each 
line was swept into place to report on its position. Considerable difficulty was ex- 
perienced in locating the lines correctly at the great depth in which the vessel lay. 
The diving on this job established a new record. The Bureau of Construc- 
tion and Repair had been experimenting with deep-sea diving for some time prior 
to the loss of the F-4. It so happened that these experiments, together with the 
development of the special equipment needed, were brought to successful termi- 
nation just before the accident. A party of specially trained men was sent to Hono- 
lulu from the New York Navy Yard, where the experimental work had been done. 
After the first few dives it was realized that the divers would not be able to 
do manual work at this great depth, because of the extreme exhaustion following 
such work. This is not so surprising when it is remembered that at 300 feet a diver 
is breathing air under 135 pounds pressure. The experimental work which had 
been done indicated also that it was not safe to keep divers on the bottom at this 
depth for any great length of time. On this job the men were not kept on the bot- 
tom intentionally more than from 10 to 15 minutes ata time. It was fortunately 
not found necessary to call on the divers to do manual work while the vessel was 
in deep water. Their function consisted of observing the location of the lines and 
reporting on the steps necessary to bring them into the positions desired. Their 
services in this connection were invaluable, as it would not have been possible to 
have adjusted the slings without their reports. 
All four hawsers were finally swept into position and were transferred to the 
scows. Some time had elapsed since the first hawser had been placed under the 
submarine, consequently this first line was no doubt considerably chafed before 
lifting operations were started. Such impairment was considerably augmented at 
just this time by bad weather, which increased the motion of the scows and dredge. 
After lifting about 12 feet and towing inshore a corresponding amount, one of 
the galvanized hawsers parted. On being brought to the surface it was quite evi- 
dent that the stranding had occurred at the bilge keels. Its replacement was some- 
