TOL. LXXIII.] PHILOSOPHICAL TRANSACTIONS. 4 1 C) 



( — 40) as when quicksilver froze in the glass cylinder, Mr. H. was of opinion 

 it would congeal by this simple method in very cold weather, and a long con- 

 tinued application of a proper degree of cold by the mixtures. 



Exper. 9 was made Feb. 22, 1/82. While Mr. H. was attending on the 

 5th experiment, and had removed the instruments into a 2d mixture, the former 

 one by this means being unemployed, he put into it a gallipot (the same as used 

 in the 8th experiment) with about 4- of a pound of quicksilver, and let it remain 

 immersed in the mixture about half an hour, and finding, by touching with a 

 quill, that part of it was congealed, he drew the gallipot out, it being previously 

 slung with a string, and decanted off the super-incumbent mixture and fluid 

 quicksilver ; the remainder, about -§- of the whole quantity, remained solid in 

 the gallipot ; the internal surface remained every where very rough and white, 

 shining like an old silver spoon long in use and having lost its polish. Part of 

 it became fluid in a few minutes ; and imagining it afforded a fine opportunity of 

 confirming what had before appeared to be the freezing point of quicksilver, he 

 put a mercurial thermometer f, which then stood at 34°, into the part of the 

 quicksilver in the gallipot, which was just thawed, and it subsided directly to 

 — 40°, and became stationary. He repeated the same with another instrument, 

 and the result was the same. He then tried the spirit thermometer d, which 

 became stationary at 28°x ; and another spirit thermometer e, which he 

 took out of the freezing mixture, where it was at 35°, and it rose to 30° ; and 

 by comparing the spirit thermometers with mercurial ones, and also with another 

 spirit thermometer h, it appears, that 1Q° on the former is about equal to 40° 

 on the scale of both the latter. By the time these observations were taken, the 

 frozen lump was loosened in the gallipot : he turned it out, and beat it with a 

 hammer ; it yielded a dead sound and flattened, but its cohesion was very weak ; 

 for, instead of expanding into a thin plate, as in other instances when frozen in 

 the bulb of a thermometer, it crumbled to pieces, and had not that polish which 

 he had before constantly observed. Mr. H. attributed these circumstances to the 

 effect of the spirit of nitre on the quicksilver. It thawed very soon after its 

 parts were disjoined by the stroke of the hammer. 



Exper. 10 was made Jan. l6, 1782, when the quicksilver was frozen by the 

 natural cold in Hudson's Bay. The subject of this curious phenomenon was quick- 

 silver put into a common two-ounce phial, and corked. The phial was about a 

 third part full, and had been constantly standing b}< the thermometer for a 

 month past. At 8 o'clock this morning Mr. H. observed it was frozen rather 

 more than a quarter of an inch thick round the sides and bottom of the phial, 

 the middle part continuing fluid. As this was a certain method to find the point 

 of congelation, he introduced the mercurial thermometer f, and the spirit ther- 

 mometer d, into the fluid part, after breaking off the top of the phial, and they 



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