MOTIONS EXCITED IN THE PARTICLES OF THE FLUID. gj 



I may add, that, in the same degree in which they appeared wonderful to me at 

 first, do they now appear to me the necessary and most satisfactory results of ele- 

 mentary and axiomatic principles. 



In directing my attention to the phenomena of the motion communicated to 

 a fluid by the floating body, I early observed one very singular and beautiful phe- 

 nomenon, which is so important, that I shall describe minutely the aspect under 

 which it first presented itself. I happened to be engaged in observing the motion 

 of a vessel at a liigh velocity, when it was suddenly stopped, and a violent and 

 tumultuous agitation among the little undulations which the vessel had formed 

 ai-ound it, attracted my notice. The water in various masses was observed gather- 

 ing in a heap of a well-defined form around the centre of the length of the vessel. 

 This accumulated mass, raising at last a pointed crest, began to rush forward with 

 considerable velocity towards the prow of the boat, and then passed away before 

 it altogether, and retaining its form, appeared to roll forward alone along the sur- 

 face of the quiescent fluid, a large, solitary, progressive wave. I immediately left 

 the vessel, and attempted to foUow this wave on foot, but finding its motion too 

 rapid, I got instantly on horseback and overtook it in a few minutes, when I found 

 it pursuing its sohtary path with a uniform velocity along the surface of the fluid. 

 After having followed it for more than a mile, I found it subside gradually, until 

 at length it was lost among the windings of the channel. This phenomenon I 

 observed again and again as often as the vessel, after having been put in rapid 

 motion, was suddenly stopped ; and the accompanying circumstances of the phe- 

 nomenon were so uniform, and some consequences of its existence so obvious and 

 important, that I was induced to make The Wave the subject of numerous expe- 

 riments. 



It very soon began to appear probable, that the existence of this phenomenon 

 of the solitary wave mould exercise very great influence on the quantity and nature 

 oftlie resistance of the fluid to a body moving with a given mlocity, according as tlmt 

 velocity was equal to, or greater, or less than, the velocity of the wave. And on making 

 this the subject of a series of experimenta crucis, the correctness of the anticipa^ 

 tion was established, and it appeared that the velocity of the motion, of the solitaiy 

 reave had a peculiar relation to a certain well-defined point of transition in the re- 

 sistance of the fluid. 



In prosecuting the inquiries to which this discovery gave rise, I found that, 

 in every instance of progressive motion of a solid in a fluid, the displaced fluid gene- 

 rated waves of the fluid that were sent in the direction of the motion of the body, and 

 propagated with a constant velocity, which was quite independent of the velocity of 

 the motion of the body, and that the magnitude, disposition, and velocity of these 

 Toaves fm^med very important elements in the resistance of the fluid to the floating 

 body. I therefore directed my investigations to the discovery of the law of the 



