TRANSVERSE SECTIONS UPON RESISTANCE. 315 



said that the form of presentation did not bring out that effect clearly, and it was the quali- 

 tative effect that the authors had in mind quite as much as the quantitative effect. 



The data from the Michigan tank have always been issued in the form of E.H.P. or 

 W.H.P. per ton of displacement, and this paper does not depart from that custom except 

 where necessary in order to show more clearly the effect of shape of section. The cube of 

 the speed-length ratio was used for the purpose of bringing out more clearly the effect of 

 section shape, and it was realized that the results in this form would not be as convenient 

 to the naval architect as if given in the form of E.H.P. per ton of displacement. 



Mr. Robertson states that in the form in which the data are given its application is 

 limited when draught and length are changed. This is true of any system, even of the 

 one which Mr. Robertson advocates. In his paper of last year he gave the results for only 

 one draught ratio, and the application of those results is very limited. In this paper we have 

 gi\'en the results for four draught ratios with a corresponding increase in the scope of 

 application. 



The authors wish to thank all those who have spoken so kindly of the paper and hope that 

 the results may be of some value, even if each one does not find the data given in his favorite 

 form. 



The Chairman: — Do you wish to comment further, Professor Sadler? 



Professor Sadler: — I do not think I have an3d:hing to add to Professor Bragg's re- 

 marks — he covered most of the points. I think if you will read this method of plotting care- 

 fully — you probably have not had an opportunity to do so — ^you will see that the E.H.P. per 

 ton has certain advantages, and very evidently there has been some misconception as to the 

 appendix in this paper. As Professor Bragg pointed out, the illustration in the appendix is 

 simply to show the amount of error if you omitted the last part of the expression; and I 

 think his illustration of the figures obtained by this method as applied to Mr. Rigg's paper, 

 which was all done here in a few minutes on the floor, ought to be an indication that there is 

 something in the method of using the E.H.P. per ton. 



The Chairman : — ^This paper comes in that category of papers which so greatly enrich 

 our Transactions and are viewed as a great repository of facts, as the result of research and 

 study. I think that the Society is to be congratulated on having this very important con- 

 tribution presented at this session, and I am sure that you will wish to convey the thanks of 

 the Society to the authors for their contribution. 



