98 



THE EXPERIMENTS OF 1835. 



degrees of immersion, and each of the others at three, are equivalent to experi- 

 ments upon sixteen vessels of sixteen different forais. 



The forms of the vessels are she^Ti in Plate III., being projected at an angle 

 of the line of vision sin. — i = ^. The " water lines of the entrance and of the 

 run" are shewn below the projections of each vessel, as taken at successive heights 

 of 6 inches. The comparisons of form may thus be easily made. 



The principal dimensions of the vessels were nearly identical. The maximum 

 breadth at the gunwale being about 6 feet, and the length, exclusive of the hehn, 

 69 feet, there being added to this in the case of the " Wave" a cutwater or very 

 sharp part of the bow 6 feet long, and of very small capacity. 



The Wave is a vessel of very peculiar form. My observations on the nature 

 of the resistance of fluids in 1834 suggested a form of least resistance. The 

 Wave was built of that form, and answered fully, and even surpassed the expec- 

 tations I had formed of the facility of her motion. The lines of entrance are pa- 

 rabolic tangent arcs, having a point of contrary flexure between the maximum 

 transverse section and the stem. The run is formed of elliptical arches, and is 

 by no means so fine as runs usually are. It has long been matter of observation 

 with me, that the maximum resistance to a vessel of ordinary form is experienced 

 in the immediate vicinity of the stem, — that the water there is thrown aside with 

 a velocity much gi-eater than is requisite to remove the particles from the portions 

 of space to be passed over by the succeeding points of the bow. This " head of 

 water" at the bow, instead of being merely thrown aside, is also thrown upward 

 and forward, so as very much to increase the resistance beyond what appears ne- 

 cessary for the transit of the vessel. It occurred to me as probable that a form 

 of vessel might perhaps be obtained, which would not at any given velocity raise 

 a head of water above the level, but merely give to the particles displaced the mi- 

 nimmn possible of lateral motion required to permit the transit of the vessel. The 

 theoretical law of least displacement, which I imagined gave me the equation of a 

 curve, which appeared to me to be a curve of minimum resistance. That this 

 curve would be the curve of least resistance I could not a priori determine ; but 

 it appeared to me that an experimentum crucis might decide the question after 

 the vessel was built. The experiment was simply to give the vessel a very high 

 velocity, such as 17 miles an hour, and if it should then be found that no particle 

 of water had any motion communicated to it except simply what was necessary 

 for the passage of the vessel, if no spray were thrown up before the vessel or dashed 

 aside by the prow ; if, in fact, the vessel, on entering smooth water, should pass 

 into it leaving the surface still unrufiled, and producing no motion among the par- 

 ticles but what was the necessary result of mere repletion, by the presence of an 

 additional body, then I should be warranted in denominating such a body the 

 solid of least resistance. This experiment was actually tried. The vessel was 



