56 THE DETERMINATION OF THE RESISTANCE OF SHIPS. 



water maximum as well as at that maximum. It may often be that an apparent sac- 

 rifice at normal speed is no sacrifice at all, but really a decided gain in coal burned 

 per annum in a seagoing ship, particularly a transoceanic or great coastwise trader. 

 A paper by E. S. White before the Northeast Coast Institution (191 2) is well 

 worthy of study in this connection. 



EFFECT OF SHOAL WATER. 



This subject has come to the front recently in practice as well as in theory. 

 Torpedo-boat destroyers have furnished the most interesting cases, and the subject 

 is worth very serious consideration by those responsible for the performance of 

 vessels running in shoal bays, rivers and lakes. The literature on the subject 

 gradually accumulates and we are now in possession of a very considerable 

 amount. 



Admiral Taylor refers extensively to the subject in his Manual, the historical 

 data therein give credit to the earlier investigators, and numerous references will 

 be found in the bibliography of this paper. 



It is not too much to say that knowledge of the effects, both bad and good, of 

 shoal water is absolutely necessary to the proper running of destroyer trials, and 

 no less so for the designing of shoal-water vessels. It will pay those charged with 

 running big vessel trials to be very careful where they run them. 



On a recent trial of a 400-foot vessel drawing 19 feet and of 15 knots speed 

 the performance at sea in smooth water was materially better than on the measured 

 course, due to deeper water as well as to the absence of the necessity for fre- 

 quently turning to run over the course, the reduction in horse-power being about 

 4 per cent. 



In a destroyer trial at 24 knots it was found that in 15 fathoms the power re- 

 quired to maintain standard revolutions was materially higher than on standard- 

 ization and that on going off into deep water this at once changed. 



Besides the guidance to be obtained from Taylor's Manual, his T. S. N. A. 

 paper of 19 13 on relative resistances of models with constant block and other co- 

 efficients varied contains valuable data. Baker's new book has a chapter devoted to 

 shoal and restricted waterways that is extremely useful. Canals are an important 

 part of shoal-water navigation, and the value of special consideration was empha- 

 sized before the Royal Society of Edinburgh as far back as 1840. Much work has 

 been done before and since, especially in connection with the navigation of French, 

 British, German and Dutch canals. 



The navigation of the Nile and similar rivers has received special considera- 

 tion for centuries. 



Professor Sadler has carried out valuable experiments at the University of 

 Michigan, his 191 1 T. S. N. A. paper giving information on merchant ship forms 

 being worthy of careful study. 



Hudson River boats have received, to their no small benefit, special considera- 



