148 CHANGE OF SHAPE OF RECENT COLLIERS. 



center being located over a punch mark on the plate of the breast hook. The transit 

 was sighted on a permanent target located at the after end of the deck house, and 

 the heights were observed by a measuring rod held vertically on each of the hatch 

 cover supports which were used as the observing stations. 



Table 4, Plate 84, shows some observations made on the collier Nereus, built 

 by the Newport News Shipbuilding and Dry Dock Company, and though the method 

 of observing was somewhat different, and the resultant curves (Plate 88) were 

 differently plotted, a comparison with the other vessels is interesting. 



The Nereus is in general similar to the Orion and Jason, except that she is 

 10 feet shorter and is built with the ordinary transverse framing. No sights were 

 taken before launching, but a line was run when the vessel was practically com- 

 plete. A second set of sights was taken in dock, and on the assumption that she 

 had straightened out, this latter set was then used as establishing the datum line ; 

 and the curves shown on Plate 88 were plotted for hog and sag, although in Table 

 4, Plate 84, all the readings were taken as sag. 



In conclusion, I wish to express my obligations to Mr. T. M. Cornbrooks, 

 Chief Engineer of the Marine Department of the Maryland Steel Company, as it 

 is largely due to the interest in this matter taken by him and by his assistants that 

 these observations were made. 



DISCUSSION. 



The Chairman : — Discussion on this paper, No. 12, "Change of Shape of Recent Col- 

 liers," is now in order. 



Naval Constructor J. G. Tavvresey, Member: — It has been my fortune to have 

 had to do some work along the lines considered in this paper, and as I found a tendency 

 in some quarters to regard it as a needless refinement, I am somewhat pleased to find the sub- 

 ject treated in this paper and brought before the Society. I wish that the author had gone on 

 and shown us a way to get around the difficulties which he brings out in the paper. 



It is true that vessels bend due to loading and due to other causes, and that the bending 

 is a great deal more in some classes of vessels than in others. Colliers are mentioned in this 

 paper. The vessels I had to deal with were torpedo-boat destroyers. Then we have car 

 floats, floating dry-docks and other structures. I found on the destroyers, which were of 

 less length than the colliers, quite as much change in shape as is reported in this paper. 

 That change was found to be due to the loading, but the loading would not account entirely 

 for it, and further investigation showed that there was a very considerable change due to 

 differences in temperature. The change due to the difference in temperature was, for the 

 range of observation made, two and sometimes three times as much as that due to the load- 

 ing. The loading in a destroyer, you must remember, is the weight of her machinery and 



