66 FLOATING DRY DOCKS IN THE UNITED STATES. 



a foot into the water. Eacli 'Camel' was divided into two parts, a lower 

 hold and between decks." 



It is to be noted that the forward end of this floating dry dock is 

 closed with a structure similar to a vessel's bow and it has been asserted 

 that the name "Camel" originated from the fact that the first one of these 

 sections was constructed from a vessel of that name. 



Note. — The writer was in Seattle on March 6, 191 1, and had the opportunity of examining the interior 

 of the Heffernan Dry Dock, previously referred to in this paper, while carrying the steamer Victoria, 360 

 feet in length with a displacement of 5,000 tons. The dock was entirely pumped out, as this ship represented 

 the maximum lift. 



The examination extended through several compartments to the center bulkhead. All timbers were 

 sound and there was no sign of deterioration from marine worms or any other cause. 



DISCUSSION. 



Mr. Horace H. Thayer, Jr., Member: — Mr. Chairman, if it is in order, I 

 would like to ask Mr. Donnelly what his idea is with regard to a composite pontoon. 



Mr. DonneI/Ly: — I have given the matter of composite construction con- 

 siderable thought and study and have always foimd a great difficulty in obtaining 

 a proper contact between the steel and wood members; that is, if the amoimt of 

 steel is limited in direct proportion to its strength, I have found that the bearing 

 contact with the wood is not sufficient to properly transmit the strain. In other 

 words, a crushing action of the w^ood would take place. 



Another difficulty, and perhaps the most serious, has been the greater tendency 

 to rust at the contact of the steel and wood. This fact has been specially brought 

 out in the experience of the John N. Robins Co. in repairing vessels, it being a 

 usual experience to find the steel work tmder wooden decks very much corroded. 



In designing the wooden pontoons and steel wings, particular attention was 

 given to the matter of contact between the bottom of the wings and pontoons. 

 To provide against possible corrosion of the wings an additional steel plate -| inch 

 thick and 12 inches wide was added and, to eliminate the direct contact as far as 

 possible with the wood, the joint was made with canvas and red lead, as referred 

 to in the paper. 



I am aware that there have been a number of composite floating dry docks 

 built and would very much appreciate any contribution by the members having 

 a definite knowledge of them. 



Civil Engineer A. C. Cunningham, U. S. N. (Communicated) : — In the 

 combination of wooden sectional pontoons with steel side walls, Mr. Donnelly 

 has secured a floating dry dock of comparatively low first cost, and moderate costs 

 for maintenance and repairs. These are essential features in a commercial dock 

 which, to be a success, must give a good return on the investment. A commercial 

 dock must be out of commission as Uttle as possible, and Mr. Donnelly's combina- 

 tion also tends to this condition. To prevent serious deterioration, a dock with 



