44-8 PHILOSOPHICAL TRANSACTIONS. [ANNO 1783. 



cold recorded by Dr. Pallas began to abate on the 7th of December in the even- 

 ing; but more than a day after, that is, on the Qth in the morning, it became 

 so intense at Irkutsk as to freeze quicksilver. An account of this phenomenon, 

 sent by Lieutenant-general Von Brill, the governor, was published by Dr. Pallas 

 in his journal, and M. Georgi, one of the associates in this expedition, after- 

 wards collected some further particulars. It appears, that about 4 in the morn- 

 ing, the quicksilver was found frozen in the barometer and thermometer, its 

 upper surface being irregularly broken. In the former of these instruments the 

 mercury stood at 28 inches 7 lines, and the broken appearance extended through 

 a space of about 5 lines from the top downward: when it came to melt a few 

 hours afterwards, it rose to 1Q inches 7 lines, which difference of height was 

 probably in part at least an effect of the contraction it undergoes in freezing, its 

 greater specific gravity in the congealed state making it stand proportionably 

 lower. In the thermometer, part of the mercury had stuck at — 41°; and im- 

 mediately under — 50° an empty space was left, equal to 1 1 degrees of the scale. 

 This observation therefore determines almost precisely the freezing point; for 

 none of the quicksilver could have adhered in the tube so high as — 44°, unless 

 it had congealed before it sunk below this point, and consequently before the 

 cold exceeded this degree. And that the mercury was really frozen became evi- 

 dent afterwards; for about 11 in the forenoon, as the air got warmer, it was 

 found to have all subsided into the bulb, the small threads in the tube melting 

 down into the vacuity left there, out of which it did not rise again till near 1 

 hours had elapsed. 



As the cold of America is well known to exceed that which prevails under the 

 same latitudes in Europe, we must expect to find quicksilver freezing sponta- 

 neously in parts of that continent which do not lie very far to the northward. 

 Accordingly, besides the instance of Quebec formerly mentioned, this effect 

 takes place frequently in Hudson's Bay, even at Albany fort, where the latitude 

 is not one degree greater than in London. Mr. Hutchins, in his different situa- 

 tions at Hudson's Bay, has been constantly attentive to meteorological observa- 

 tions. During his former residence at York fort, situated near the middle of 

 the Bay in hit. 58 n. he was not provided with any thermometer graduated more 

 than 70 or go degress below the cypher : but he remarked, that " the quicksilver 

 frequently sunk into the bulb," especially after having been stationary at — 55° 

 or — 57°, and that it afterwards used to ascend to " about — 30°, indicating a 

 greater degree of heat than before it fell." These phenomena were clearly owing 

 to its congelation, adhesion in the tube, and subsequent liquefaction as the air 

 got warmer. When Mr. Hutchins went afterwards to Albany fort, and had 

 procured instruments with more extensive scales, he observed the same .inpear- 

 ances still more distinctly. His thermometers froze twice in the winter of 1774 



