TRANSVERSE SECTIONS UPON RESISTANCE. 311 



most serious criticism of the whole paper in my mind has to do with the actual quantitative 

 resuks themselves. These are expressed as already indicated, as E.H.P. upon displacement, 

 divided by the cube of the speed ratio. Now I submit that this system, which is quite novel, 

 and therefore useless for comparison purposes with any previous results, is also without the 

 one advantage claimed for it — that it is suitable for ready application by the busy naval 

 architect who does not specialize on ship resistances. This form of expression, which does 

 not follow the law of comparison, gives serious differences for very limited changes in 

 draught, and is impossible of application for any important changes in length, and therefore 

 the data presented are very limited in their application; even a 12 per cent variation in length 

 above or below that at which the results are given shows 1 per cent variation in resistance; 

 and otlier draughts than those presented could only be obtained by the use of cross curves. 



Doctor Sadler and Professor Bragg must be aware that the advantage of experimental 

 tank results is largely that it enables a designer to choose the minimum dimensions of a 

 vessel for a given duty, and that the economies so effected are usually greater than the econo- 

 mies gained by a slight variation in the resistance of a vessel of fixed size. Any investiga- 

 tion along the lines of variation of ship dimensions must be carried out on a different basis 

 than that on which these results are presented. Anyone who has had any experience with the 

 Froude "C" Constant System will realize how very much superior it is to the one here used. 



I hope the authors of the paper will understand that in spite of this rather stringent criti- 

 cism the paper appears to me as being one of the greatest value, and I join heartily in con- 

 gratulating the Society in obtaining this admirable contribution. 



Mr. E. H. Rigg, Member of Council: — It is in order to once more call attention to the 

 very valuable work which Professor Sadler and his colleague, Professor Bragg, have done 

 in the cargo-boat field. We heard this morning of the importance of economy of operation, 

 and as a practicing naval architect I want to bear witness to the fact that these gentlemen 

 have contributed to this in a very material, even if highly mathematical, way; they are stead- 

 ily publishing the results of experiments which are valuable to our profession, assembled 

 here and in other places, all tending to bring about economy of actual ship operation. It is 

 just as important to have a low E.H.P. per ton of displacement as it is to have a low fuel con- 

 sumption per horse-power developed. 



With regard to the methods of presentation, I am not going to enter particularly into 

 that discussion, which is in able hands, but I feel strongly that anything that this Society 

 could do to help standardize these methods would be welcomed by the profession at large. I 

 have talked with Admiral Taylor, Sir Archibald Denny, and Mr. Robertson; and on one 

 occasion, some years ago, was rash enough to venture some remarks of my own on desirable 

 methods of presentation of results. The proper solution seems to be that the tanks should 

 each retain their own working methods but adopt a common standard for publishing results; 

 that appears to be the general opinion which I gathered in talking the matter over with gentle- 

 men intimately connected with experimental tank work. 



Mr. Hugo P. Frear, Member of Council : — Doctor Sadler, as I understand it, has taken 

 models on which exhaustive tests had previously been made to determine the best longitu- 

 dinal distribution of displacement and found that by modifying the distribution of displace- 

 ment up and down a considerable saving could be made. It is not my intention to discuss 

 at length the body of the paper, because I have not given it sufficient study and there are 

 others here who have and are carrying out that part of the program very well. 



