VOL. LXXIII.] PHILOSOPHICAL TRANSACTIONS. 44Q 



and 1775, and 3 times in that of 1777 and 1778; and in every instance, except 

 one, the mercury sunk hundreds of degrees just as the cold began to abate. The 

 last of these observations is rendered remarkable by the descent of the quicksilver 

 to — 490, the greatest ever known by natural cold, and probably very near its 

 extreme term of contraction by freezing. In 1782, also, Mr. Hutchins's ther- 

 mometers, together with some quicksilver in a phial, again congealed in the 

 open air, and exhibited similar phenomena, as appears from the account of his 

 experiments. 



Fortunately in these instances of intense cold at Albany fort, attention was 

 paid not only to the mercurial thermometers, but likewise to one made of spirits, 

 whose relative movement has been ascertained by comparison. This instrument 

 while the others were 3, 4, or almost 500 degrees below O, never sunk farther 

 than to a point which corresponds with — 46° of a standard mercurial thermo- 

 meter. Hence it would have been easy to infer, both that the quicksilver actu- 

 ally congealed on these occasions, and that the degree of cold necessary for such 

 an effect does not exceed — 46°. That the most intense cold of Hudson's Bay, 

 during a series of several years, went so little below the point of mercurial con- 

 gelation, well deserves to be noticed; and as it seems to be seldom greater in 

 Siberia, at least in the parts visited by Gmelin or Pallas, the effects being not 

 more violent, perhaps we are authorized to conclude, that the extreme of artifi- 

 cial cold, produced by snow and nitrous acid, corresponds pretty exactly with 

 the extreme of natural cold in the most rigorous climates which can well be in- 

 habited. 



Again, to return to Europe. In the beginning of the year 1780, M. Von 

 Elterlein, of Vytegra, froze quicksilver by natural cold, and sent an account of 

 his experiment in a letter to the late Prof. Guldenstadt, then at Petersburg, to 

 the following purport. "On the 4th of January, 1780, the cold having in- 

 creased to — 34° that evening at Vytegra, I exposed to the open air 3 oz. ot very 

 pure quicksilver, in a China tea-cup, covered with paper pierced full of holes. 

 Next day, at 8 in the morning, I found it solid, and looking like a piece of cast 

 lead, with a considerable depression in the middle. On attempting to loosen it 

 in the cup, my knife raised shavings from it as if it had been lead, which 

 remained sticking up ; and at length the whole separated from the bottom of the 

 cup in one mass. I then took it in my hand to try if it would bend ; it was like 

 stiff glue, and broke into 1 pieces ; but my fingers immediately lost all feeling, 

 and could scarcely be restored in an hour and a half by rubbing with snow. At 

 8 o'clock a thermometer, made by M. Laxmann of the Academy, stood at — 

 57°; by half after Q it was risen to — 40°; and then the 2 pieces of mercury, 

 which lay in the cup, had lost so much of their hardness that they could no 

 longer be broken or cut into shavings, but resembled a thick amalgam, which, 

 vol. xv. 3 M 



