428 PHILOSOPHICAL TRANSACTIONS. [ANNO J/83. 



then dipping the ball of the thermometer into the unfrozen part, observed what 

 degree it stood at. These experiments agree with the former in showing the 

 freezing point to be — 40° on the two mercurial thermometers ; and also show 

 what degree on the spirit thermometers answers to it, namely, '2Q% or 28°i- on 

 d, and 30° on e ; for in these two experiments the spirit thermometers also were 

 dipped into the frozen quicksilver. 



In all the experiments therefore, tried with the thermometer g, the freezing 

 point came out — 40°. In those tried with f, it came out either — 40°, or about 



— 40°i ; so that as it appears from Mr. Hutchins's table of comparison, that f 

 stood at a medium a quarter of a degree lower than g, the experiments made 

 with that thermometer also show the freezing point to be — 40° on g ; and as it 

 appeared from the examination of this thermometer after it came home, that 



— 40° on it answers to — 38-S-, on a thermometer adjusted in the manner re- 

 commended by the committee of the k. s., it follows, that all the experiments 

 agree in showing that the true point at which quicksilver freezes is 38°-§-, or in 

 whole numbers 39° below 0. 



It appears then, that the point at which quicksilver freezes has been determined 

 by Mr. Hutchins in different ways, all perfectly satisfactory, and all agreeing in the 

 same result. In the first 3 experiments the thermometer was surrounded by 

 quicksilver, which continued freezing till it became solid. In the 6th experiment 

 the quicksilver with which it was surrounded continued slowly melting till the 

 whole was dissolved ; and in both cases the thermometer remained stationary all 

 the while at what we have just said to be the freezing point. In the gth and 

 10th experiments, the ball of the thermometer was dipped into quicksilver, pre- 

 viously frozen and beginning to melt, as usually practised in settling the freezing 

 point on thermometers, and agreed in the same result, the quicksilver in the last 

 experiment being frozen by the natural cold of the atmosphere ; and in the 

 former, by being immersed in, and in contact with, a freezing mixture ; so that 

 this point appears to be determined in as satisfactory a manner as can be desired ; 

 and the more so, as it seems impossible that experiments should be made with 

 more care and attention, or more faithfully and circumstantially related, than 

 these have been. The 2d and 3d experiments also show, that quicksilver, as 

 well as water, can bear being cooled a little below the freezing point without 

 freezing, and is suddenly heated to that point as soon as it begins to congeal. 



On the contraction of quicksilver in freezing. — All these experiments prove, 

 that quicksilver contracts or diminishes in bulk by freezing ; and that the very 

 low degrees to which the thermometers have been made to sink, is owing to this 

 contraction, and not to the cold having been in any degree equal to that shown 

 by the thermometer. In the 4th experiment the thermometer a sunk to 



— 450°, though it appeared by the spirit thermometers that the cold of the 



