HYDROSTATICS. The science which treats of the laws regulating the motions, pres sure, gravitation, and equilibrium of fluid bodies, particularly water, and also of solid bodies immerged therein. This science is divided into three branches, namely, hydro statics, properly socalled, which treats of fluids in an equilibrium, their density, gravity, esc. ; hydraulics, which treats of fluids in a state of motion ; and pneumatics, which treats aelae, tic fluids. These two last branches will be found explained in their respective places. The first branch of hydrostatics engaged the attention of Archimedes, who appears to have first attempted to determine the spcific gravi ty of bodies, in consequence of the following circumstance. Hiero, king of Syracuse, having reason to suspect that a goldsmith, whom be employed to make him a crown of gold, had adulterated it with a quantity of sil ver, be requested Archimedes to detect the cheat. Accordingly, this philosopher procured two masses of gold and silver of equal weight with the crown, which he immersed in a vessel ,full of water, at the same time carefully no ticing the quantity of water which each dis placed; after which he immersed the crown of gold also in the same vessel, and by compar ing the quantity of water which flowed over each time, he was enabled to ascertain the pro , portions of gold and silver in die crown. He
is said to have been led to this idea by otserv ing on one occasion, whilst he was bathing, [that as he immerged his body, the water ran over the bath, whence he concluded that the water which ran out when his whole body was immerged, was equal in bulk to his body ; and on the same principle he considered that if the crown were altogether of gold, the ball of gold, being of the same bulk as the crown, would, when immersed, raise the water just as high as the crown immersed, but if it were wholly of silver, the ball of silver being immersed would raise the water no higher than the crown immersed ; and if the crown was of gold and silver mixed in a certain proportion, this pro portion would be discovered by the height to which the crown would raise the water higher than the gold and lower than the silver. The authors who have treated further on this sub ject may be found under the article HYDRO DYNAMICS.