VOL. LXXIII.] PHILOSOPHICAL TRANSACTIONS. 443 



cury sunk at once to — 114°, after having been stationary two whole days at — 

 45°. The last observations of M. Gmelin's, in which quicksilver froze, were 

 made on his return homeward in a part of Siberia, much nearer the confines of 

 Europe. During the month of December 1742, as he was passing over that 

 branch of the Ural or Riphaean mountains which runs between Verchoturie and 

 Solikamsk, about the 5gth degree of n. lat. and scarcely 6o degrees e. of Green- 

 wich, his thermometer sunk to — 41°, — 70°, and at length into the bulb, 

 though it was graduated to q6° below O. The same appearance of air-bubbles 

 which he had so frequently remarked in such great descents of the thermometer, 

 puts it beyond doubt that the quicksilver was frozen. This event furnished a 

 very striking proof of the force of habit in reconciling men to hardships, which 

 in their common course of life are thought intolerable. Professor Gmelin, who 

 had now been g years in Siberia, not only bore to travel in this excessive cold, 

 but also, in order to ascertain the height of the mountains he traversed, em- 

 ployed himself in observing a barometer, while the quicksilver was freezing in 

 his instruments! 



These are the principal of Dr. Gmelin's thermometrical observations. He 

 collected many more, part of which were destroyed by fire or other accidents, 

 and the remainder seem to contain no further information. They were considered 

 by him as demonstrating the cold of Siberia to exceed that even of the most 

 northern parts of Europe near 100°, an opinion which has since been almost uni- 

 versally adopted; whereas we have in fact no proof that the difference of climate 

 amounts to so much as the variation between one winter and another. At Yeni- 

 seisk, where the cold was so intense in 1735, it does not seem to have ever been 

 sufficient to freeze a thermometer in the winter that M. Gmelin spent there 4 

 years afterwards; and it will soon be shown that quicksilver has congealed more 

 than once in Europe. All that we are authorized to conclude therefore, with 

 respect to the Siberian climate, is, that the cold there not unfrequently exceeds 

 the degree indicated by — 39° of a standard mercurial thermometer. 



About the time when the quicksilver was exhibited frozen to Prof. Gmelin, 

 near the extremity of Asia, without overcoming his prepossession, M. Mauper- 

 tuis and his associates saw the liquor congeal in their spirit thermometer at 

 Tornea in Lapland. Their mercurial thermometer sunk at the same time to — 

 37° of M. de Reaumur's scale; which, if the instrument was exactly graduated 

 according to that philosopher's original idea, would undoubtedly show that the 

 quicksilver froze, as it corresponds with — 51° of Fahrenheit. But the inaccu- 

 racies in constructing M. de Reaumur's thermometers have been so great, that 

 I think no dependance can be placed on this observation, especially as it does not 

 appear to have been attended with any extraordinary phenomenon. The same 

 objection holds good with regard to the observations made by M. Gautier at 



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