METHOD OF CONSTRUCTION OF CONCRETE SHIPS. 27 



necessary that it be handled more carefully than a steel ship when in harbor. It is 

 possible some means will be found to obviate this weakness. 



The future utility of the concrete ship depends upon two factors — one, its dur- 

 ability, and the other its economy of operation as compared with wooden and 

 steel ships. 



The final durability of the concrete ship can only be determined by years of 

 experience, but it is quite probable that two or three years of operation of the ships 

 now building will furnish some indication of the life which may be anticipated. 



The economy of the concrete ship as compared with steel and wooden ships, as- 

 suming that it will have an equal life, depends upon the relative first cost and the 

 difference in the cost of propulsion due to the variation in the tare weight of the 

 hulls for equal carrying capacity. The ratio of the deadweight carrying capacity 

 to the total displacement for the lightest concrete ship so far constructed is 0.56, 

 which is about equal to the wooden ship and much less than the steel ship. For ships 

 of the same dimensions the concrete ship has a greater capacity for measurement 

 cargo than the wooden ship, and only a slightly less capacity than the steel ship. For 

 ships of the same deadweight the concrete ship has much greater capacity for meas- 

 urement cargo than either steel or wooden ships. The relative economy of the 

 several types of ships will, of course, vary, depending upon the type of cargo 

 handled, length of voyage, and percentage of time in port. 



When the concrete ship has demonstrated its durability, many situations will be 

 found where it will prove more economical than either wood or steel in spite of its 

 greater hull weight, which probably can never be entirely overcome. 



DISCUSSION. 



Ths President: — Gentlemen, you have heard Paper No. 1, entitled "Methods Em- 

 ployed in the Construction of Concrete Ships," by Mr. R. J. Wig, Visitor. It is much to 

 be regretted that Mr. Wig is absent, because I dare say there are a good many questions 

 the members would like to ask. In Mr. Wig's absence the Chair will be glad to have 

 such discussion of the paper as may be desired by the members present. 



Is there any comment on the paper? Unfortunately, the paper is among those which 

 came to hand very late. In fact, it only reached us yesterday, and I presume that very few 

 of our members have had an opportunity to read it through. I glanced through it very 

 hurriedly a few moments ago, and I note that Mr. Wig himself suggests the crucial test in 

 the paragraph on page 27, in which he says : "The future utility of the concrete ship de- 

 pends upon two factors — one, its durability, and the other its economy of operation as com- 

 pared with wooden and steel ships." I might add a further condition, and that is its relative 

 economy in construction as compared to the others. These are all factors whose value time 

 alone can properly demonstrate. 



