i6 EXPERIMENTS ON THE EULTON AND THE EROUDE. 



study the matter further, but I believe we all can go ahead with more confidence 

 on a new design by studying all the experiments which Professor Peabody has made. 



Mr. W. T. Donnelly, Member:— As to the relation of handUng tow-boats with 

 coarse pitch and relatively small number of revolutions, it should be kept in mind 

 that when working slow or starting up in handling a vessel, a steam tow-boat has 

 stored up a large surplus of power. This perhaps is not reaUzed by the captain 

 or engineer, but it is an undoubted fact, and under those conditions the coarse 

 pitch wheel in connection with the stored-up energy of the steam boiler can carry a 

 very large overload. 



It is probably a fact that efficiency under such circumstances would be much 

 below that shown by Professor Peabody's experiments, but efficiency under the 

 conditions referred to, that is, the nosing about of vessels by a tug, is something 

 that the captain and engineer of the tug would have Uttle or no sympathy with and 

 relatively would be of little or no importance. 



As was said by the last speaker, there is no question but that a coarse pitch 

 screw handles the boat quicker and better. We can readily understand that 

 because it will absorb much more power, and there is nothing in the experiments 

 conducted by Professor Peabody which would in any way contradict these facts, 

 and in all probabihty both the statements of the practical man and the scientific 

 man are true when properly understood. 



There is certainly no question but that, as engineers, we must weigh and 

 measure to determine the energy we are using and results can be predicted in no 

 other way. 



It is equally important to consider carefully the experience of the practical as 

 well as that of the scientific man, and it is certain that they cannot reach the best 

 results without thoroughly understanding each other. Most of their differences 

 arise from a misunderstanding of the terms and expressions used, each being 

 unfamiliar with those of the other. 



The President: — Are there any further remarks on this paper? If not, I 

 will ask Professor Peabody to close the discussion. 



Professor Peabody; — I was, in anticipation, prepared for objections to 

 any or all of my conclusions in the paper just presented, but I cannot quietly 

 submit to the imputation that because the work is done in a scientific manner 

 it therefore cannot be practical and is to be set aside by anyone who says 

 "This disagrees with my experience. " I claim that in this paper there is a wider 

 variety of experience than can be found even in long years of experience in a narrow 

 line of practice when only one type of propulsion is used and cannot be varied. 

 The fact that a slow engine was found desirable in a given case is no proof that 

 with proper design a high-speed engine cannot be used. At the same time I appre- 

 ciate that the designer is limited by his conditions, including the prejudices of those 

 who are to handle the boats, and this is recognized in the paper. 



