VOL. LXXIII.] PHILOSOPHICAL TRANSACTIONS. 417 



ing still at 40° or 41°. He then hung it up in the open air, and looked at it 

 only now and then. At 10 h 47 m , after being exposed to the air near an hour, 

 only a small quantity of the surface of the quicksilver was fluid, the rest was a 

 frozen globe resembling a ball of polished silver ; the thermometer inclosed was 

 still at 40°. At ll h 4 m he observed a segment of a globe of solid quicksilver; 

 in the inside was a concavity, made probably by the bulb of the thermometer. 

 The thermometer was still at 40°, which undoubtedly is the freezing point of 

 quicksilver, as in this instance part of it was frozen, and part solid. He with- 

 drew the thermometer, poured out the fluid quicksilver, and returned the ther- 

 mometer into the cylinder, shortly after which it was at 37°, and the frozen seg- 

 ment was then fluid. 



The apparatus g was hanging in the open air at 40°, and put into the same 

 freezing mixture at 9 h 51 m , on which it sunk instantly to 210°, at which degree 

 it was stationary at Q h 53 m , when it was taken out of the mixture perfectly solid. 

 At 10 h 6 m it had subsided into the bulb. Finding the quicksilver in the enclosed 

 thermometer sink instantaneously as soon as the apparatus was put into the 

 freezing mixture, it was taken out immediately to view it, and replaced in a few 

 seconds of time. The quicksilver was not yet solid, but was in frozen pieces of 

 irregular shapes, resembling ice that had been broken to pieces by concussion in 

 a pail of water, but with this remarkable difference, that as ice swims on the 

 water, the frozen quicksilver subsided in fluid quicksilver, and the segment of 

 ice, found in the thermometer f was also at the bottom of the cylinder, and re- 

 mained there after decanting the liquid quicksilver from it. Hence we may con- 

 clude, that cold increases the gravity of quicksilver, as indeed must be the case, 

 since it is certain it occupies less space in a solid than in a fluid state. 



Experiment 7th was made Jan. 22, 1782. From the 6th experiment Mr. 

 H. was induced to think, that the nearer the temperature of the atmosphere ap- 

 proached to the freezing point of quicksilver, so that a great degree of cold 

 might be communicated to the bulb of a thermometer and yet the quicksilver in 

 the tube remain fluid, would be the properest time for ascertaining in this 

 manner to what degree quicksilver will contract by the application of cold. With 

 this view this 7 th experiment was made : the several thermometers from a to h 

 were as follow, before beginning ; a 38, b 36, c 33, d 24, e 1A\, p 33, g 33, 

 h 37. Those used in the experiment were c, d and h. The first was to show 

 the descent of the quicksilver ; and the other two, which were spirit thermo- 

 meters, were employed to show the corresponding contractions of the two sub- 

 stances, quicksilver and alcohol. After above an hour's attendance on them, the 

 quicksilver fell to 1367° below the cypher; and he supposed, by changing the 

 mixture for a fresh one, he should get it still much lower. He made another 

 accordingly, and removed the instruments into it. The quicksilver rose, as was 



vol. xv. 3 H 



