238 



3. Notice regarding some points in Hydrodynamics that 

 have been misunderstood. By Mr Scott Russell. 



This notice is occasioned by a passage in the fifth volume of the 

 Transactions of the British Association, page 251, in which Pro- 

 fessor Challis claims for himself the merit of having been the first 

 who deduced from mechanical principles the anomalous emergence 

 of a floating body from a fluid at high velocities, and where he ad- 

 duces Mr Russell's experiments in support of the method of rea- 

 soning he has there adopted. Previous to the publication of his 

 paper, JMr Russell had given the theoretical explanation of the phe- 

 nomenon, and had also adduced experiments in support of that ex- 

 planation at the meeting of the British Association in Edinburgh. 

 The object of this notice is not, however, to argue the claim to 

 priority of discovery, which the author of this notice considers of 

 little importance, provided the truths accordant with the pheno- 

 menon have been rightly determined ; but his present aim is to re- 

 move certain misconceptions into which Professor Challis has fallen 

 in regard to the nature of the phenomenon he has explained, — mis- 

 conceptions of a grave nature, not merely as regards theory, but 

 which are likely to produce a most injurious efi'ect upon the prac- 

 tical application of these principles ; for it appears that practical 

 men have also been led astray by the authority of Professor Challis's 

 name, and the imposing apparatus of calculus, which they were not 

 able either to understand or expose : and, accordingly, we find the 

 author of the last paper in the first volume of the Transactions of 

 the Institute of Civil Engineers misled by Professor Challis, and a 

 Mr Woolhouse, who has edited a second edition of Tredgold on 

 the Steam-Engine, adopting similar views. 



Now, as Professor Challis had adduced Mr Russell's researches 

 in support of his views, he is thus brought in for a share of respon- 

 sibility for the defect of those views, and has therefore felt it in- 

 cumbent on him to place the question in its true light. 



The following is the passage in Mr Challis's report : 



" The circumstance of floating bodies rising vertically when 

 drawn with considerable velocities along the surface of the water, 

 having attracted attention a few years ago, induced me to try to 

 explain the fact on mechanical principles ; and, accordingly, in a 

 paper published in the Cambridge Philosophical Transactions, I 

 have entered on a mathematical investigation, which accounts for 

 such a fact, and shews that, when the velocity of draught is uni- 



