FLOATING DRY DOCKS IN THE UNITED STATES. 71 



do or should originate in the interior of pontoons. It has been said that nine- 

 tenths of man 's trouble is due to his stomach and — to press the analogy further — 

 the interior of pontoons can be no more easily dispensed with. 



Mr. Donnelly has solved the problem, within the limits of his material, by 

 building his towers of steel and his pontoons of timber. His pontoons are immune 

 from corrosion and may be protected on the outside from the toredo, while con- 

 ditions on the inside do not favor the best work of that pest. As a commercial 

 proposition it would seem that the " Donnelly type" satisfies the long search for a 

 dock combining the advantages of a steel structure with moderate first cost and 

 reasonable upkeep charges. 



For naval purposes it is doubtful if this type will ever be adopted for the larger 

 class of ships. This for the reason that naval architects give the first desideratum 

 for warship docks as extreme stift'ness. The warship is a delicate structure and 

 should be docked on a level, and as nearly non-flexible, platform as possible. 

 This requirement necessitates the closest approach to a solid trough dock as is 

 compatible with the necessary self-docking features, and virtually eliminates all 

 types consisting of numerous short pontoon sections with separate side walls. 

 On the other hand the construction of a one-piece 35,000-ton timber floating dock 

 is obviously beyond the practical limits of timber construction. 



For the smaller class of naval vessels, such as torpedo boats, destroyers, gun- 

 boats and smaller cruisers, the combination structure offers a most satisfactory 

 facility and there is need for quite a number of such docks at the present time. 

 It might be well if every repair station were equipped with at least one small dock 

 of, say, 3,000 tons lifting capacity, for use as a relief for the larger graving docks — 

 a step that would be warranted from motives of economy as well as of strategy. 



A recent report on the condition of the floating dock Dewey discloses a consider- 

 able amount of deterioration of all exposed metal in the interior of pontoons, except 

 that part covered by bitumastic enamel, which was found to be apparently im- 

 changed. Bitumastic was placed hot, | inch thick, over all plates, shapes and other 

 metal, on the floors of pontoons and for a height of 1 2 inches upward on the vertical 

 surfaces. All other interior surfaces were covered with three coats of red lead. 

 The cost of applying bitumastic was in the neighborhood of seven cents per square 

 foot of surface covered. It may be of interest in this connection to state that 

 experience with the bitumastic solution alone has been misatisfactory in locations 

 where it has been tried, and the enamel, when placed on the outside of floating 

 structures, has proven equally unsatisfactory. Red lead and certain brands of 

 graphite paints have given the best service on exposed surfaces on the outside 

 of the structure and inside of side walls, except on decks. No satisfactory 

 protection for decks has yet been discovered but, of all those yet tried, the Ctinning- 

 ham tar paint has given the best results, and it is probable that entire satisfaction 

 might be obtained from this covering when better and more uniform methods 

 of applying it have been determined. 



The limits of this discussion do not permit specific mention of all the valuable 



