154 ON THE REVOLUTIONS 



elevation would of course be the greatest in the middle, the 

 quantity of matter in the vertical line being the least ; but there 

 is no doubt that an action of the same kind, diminishing in 

 a Inch ratio, as the distance from the centre increased, would 

 be extended all round ; the surface of the fluid being thrown 

 into the form of some species of conchoid, produced by the re- 

 volution round the vertical axjs ci of the line dee, (Plate VI. 

 fig. 1.) the highest point of which is at c, with a contrary flex- 

 ure at / and //, and going off beyond these points, in such a 

 manner as to have the original level surface of the water dhe 

 for an asymptote. This conchoidal elevation, produced in the 

 flrst moment, being just equal in bidk to the quantity of water 

 displaced by the solid mass [a a) elevated at the bcvttom. 



If this mass stopped suddenly, as would naturally happen, 

 when, in consequence of the rupture,, the protruding liquid 

 stone has found a vent ; it is evident, that every part of the wa^ 

 ter put in motion during the first moment, would tend, accord- 

 inf to the first law of motion, still to continue moving during 

 the next and following moments ; but this tendency could not be 

 everywhere effectual ; because, if all the water that rose in the 

 first moment were to rise also in the second, a vacuum would 

 be the consequence. In the second moment, then, a struggle 

 must take place between the different portions of the fluid ; 

 the middle portion, which had acquired the greatest velocity, 

 would continue to flow vxpwards, and its place not being sup- 

 plied from below, as, during the first moment, a suction would 

 be exerted downwards, upon all the surrounding fluid. The 

 consequence must be, that the rise which each particle would 

 have performed by its separate momentum, during this second 

 moment, would be counteracted by the pressure of the atmo- 

 sphere, and entirely done away at a certain distance from the 

 centre, as at /and //, fig. 2. ; beyond that limit the water would 



sink 



