THE LAWS OF FLUID EESISTANCE. 121 



of thought by which the search for improved forms is com- 

 monly directed, consists of ideas which, if the doctrine of 

 stream-lines is true, are absolutely delusive and misleading. 

 And real improvements are not seldom attributed to the 

 guidance of those very ideas which I am characterising as 

 delusive, while in reality those improvements are the fruit 

 of painstaking, but incorrectly rationalised, experience. 



I am but insisting on views which the highest mathe- 

 maticians of the day have established irrefutably ; and my 

 work has been to appreciate and adapt these views when 

 presented to me. 1 



No one is more alive than myself to the plausibility of 

 the unsound views against which I am contending ; but it 

 is for the very reason that they are so plausible that it is 

 necessary to protest against them so earnestly ; and I hope 

 that in protesting thus, I shall not be regarded as assuming 

 too dogmatic a tone. 



In truth, it is a protest of scepticism, not of dogmatism ; 

 for I do not profess to direct any one how to find his way 

 straight to the form of least resistance. For the present 

 we can but feel our way cautiously towards it by careful 

 trials, using only the improved ideas which the stream-line 

 theory supplies, as safeguards against attributing this or 

 that result to irrelevant, or rather, non-existing causes. 



1 I cannot pretend to frame a list of the many eminent mathemati- 

 cians who originated or perfected the stream-line theory ; but I must 

 name from amongst them, Professor Rankine, Sir William Thomson, 

 and Professor Stokes, in order to express my personal indebtedness to 

 them for information and explanations, to which chiefly (however im- 

 perfectly utilised) I owe such elementary knowledge of the subject as 

 alone I possess. 



