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THE RAISING OF THE DRY-DOCK DEWEY. 149 
high side to the low side through the center bulkhead, through deteriorated pipe 
connections to the various compartments and through leaky valves, and that, as 
the list increased, the corresponding flow of water also increased very rapidly, result- 
ing in that side of the dock becoming entirely submerged until it rested upon the 
bottom. 
As an indication of the amount of leakage through the center bulkhead, the 
experience in raising the dock is quite conclusive. It appears that, with a consider- 
able inclination, it was more than could be handled by a 24-inch centrifugal pump. 
Part of this was through leaky valves and defective piping, but a great portion 
must have been through defects in the bulkhead itself. The inadequacy of the 
interior bulkheads was also shown by the fact that it was impossible to raise the 
dock with compressed air, the air escaping in one case through five bulkheads, one 
of which was the center bulkhead. Bearing these facts in mind, what are the lessons 
that we are to learn and the additional precautions that we should take hereafter 
in designing similar structures? 
First, I should like to point out that the dock was provided with pumping 
machinery only on one side and that, consequently, the center bulkhead was pierced 
with many pipes, upon the integrity of which and their valves the stability of the 
structure as a whole was entirely dependent. I should lay down as a positive 
rule that no openings whatever should be made through the center bulkhead of a 
floating dry-dock and that every possible precaution should be taken to have this 
bulkhead absolutely watertight. I would call attention to the fact that it is ex- 
tremely difficult to make and maintain watertight interior bulkheads, and I should 
lay down as a second rule that interior bulkheads, as such, should be reduced to the 
smallest number. 
It was quite definitely shown by the experience in raising this dock, that the 
controlling of the pumping from a central point through piping is extremely difficult. 
I might refer to one point of the paper where it says: “No matter which 
valves were open or closed, the pump took water from the high tanks before remov- 
ing any from the low tanks.” 
I would suggest as a third rule for careful consideration, that the subdivision 
and distribution of pumping units to the different compartments of a floating dry- 
, dock is a much more reliable and desirable method than by pipes and valves. 
I would also like to point out that in this floating dry-dock there were no 
reserve chambers or compartments of a sufficient capacity to provide for the buoy- 
ancy of the structure entirely independent from these compartments used in lowering 
the docks. It would seem that there could be no good reason for this construction, 
and I would offer as a fourth suggestion that in all large floating dry-docks there 
should be provided watertight compartments entirely distinct from those used for 
lowering the dock, of sufficient capacity to carry the dock when lowered, and that 
these compartments should be provided with separate and distinct pumping machin- 
ery kept in working order and available for use whenever the dock is lowered. 
There are undoubtedly other suggestions that will occur to other members of 
the Society, and I trust that they will be heard from. 
