402 Mr. Crichton on [June, 



the French for this purpose, having been a cylinder nine inches 

 in diameter, and of the same height, must have rendered it a 

 matter of uncommon difficulty in the quantity of water neces- 

 sary. Whether this uniformity existed, at the moment of its 

 greatest apparent gravity, may admit of some doubt, however 

 carefully and constantly the thermometer may have been 

 observed; besides, air-bubbles, which it would be almost impos- 

 sible to see or remove, might have considerably increased the 

 buoyancy of the suspended solid. To estimate the compensa- 

 tions for expansion, in the above-mentioned method, is perplex- 

 ing, and for the mode by the weighing bottle is still more so; but 

 to ascertain the quantity of hygrometric humidity, which pro- 

 fusely and rapidly fixes on the exterior surface of a bottle, at so 

 low a temperature as 40, is perhaps from several causes imprac- 

 ticable. A hope of being able to assist in obviating these embar- 

 rassments, induces me to present a new method of determining 

 this point. 



Having frequently observed that a very small alteration of 

 temperature in a fluid, destroyed the precise poise of a solid in 

 that fluid, and that an extremely minute increase or diminution 

 of gravity in the solid, has a similar effect ; it was easy to per- 

 ceive, that if water is of a certain gravity just above freezing, and 

 that if it become heavier, with an increase of temperature, before 

 it reach, say for example, 50, then it is manifest, that at some 

 included degree, water must of necessity poise, or sustain, a ball 

 or solid of greater specific gravity, than it will do at any other 

 point in the supposed interval. 



My first attempt to ascertain this point, evinced, that a ball 

 which was just poised, at about 33, had the same property near 

 51 ; this gave 42 for the point of greatest density, taking the 

 half of the intervening degrees as additive to 33, or the reverse 

 from 51, since all authorities seem to agree, that the expansion 

 is the same for equal intervals of temperature, on both sides of 

 the maximum. 



It may be supposed, that to adapt a ball of the greatest pos- 

 sible specific gravity which water can sustain at its greatest 

 gravity, would be the next endeavour ; it was, but so infinitely 

 little is the variation of the gravity of water, for about a half 

 degree on either side of the maximum point, that although I 

 have, more than once, diminished the gravity of balls which 

 were too heavy, by a quantity so minute, as not to amount to 

 the GOOOth part of a grain, or just as little as I could by any 

 means grind o(F, still, on trial at the proper range of tempera- 

 tures, it was found that the mark had always been overshot. 

 This then was relinquished as a hopeless task. 



As it had not however escaped notice in the course of these 

 experiments, that the further the temperature of water was 

 removed from that of the greatest gravity, the ball rose, or fell, 

 with celerity just commensurate to the number of degrees which 



