440 PHILOSOPHICAL TRANSACTIONS. [ANNO 1783. 



spirit thermometer, and found it nearly as great as Mr. Hutchins had ever pro- 

 duced at Hudson's Bay, that is, about equal to — 45° of a standard mercurial 

 thermometer. 



The subsequent part of this narrative demonstrates, that quicksilver has very 

 frequently become solid by natural cold ; that in a few instances the effect was so 

 palpable and obvious as to strike with immediate conviction ; but that in most it 

 has never been even suspected till the present time, the strange appearances which 

 often occurred being imputed by the observers to any other rather than the real 

 cause, though they are now found to carry with them a force of internal evidence 

 which establishes the truth beyond all doubt. In enumerating these facts, Dr. 

 B. continues to pursue a chronological order. They are in general of such a kind 

 as could scarcely become an object of attention, till thermometers had acquired 

 some degree of accuracy. This did not happen till near the year 1730, and the 

 first observations which prove the freezing of quicksilver were made within 4 or 5 

 years of that period : so intimately are improvements in philosophy connected 

 with the perfection of instruments ! 



When the Empress Anna Ivvanovna had ascended the throne of Russia, she re- 

 solved to carry into execution one of the favourite ideas of her uncle, Peter the 

 Great, by sending out proper persons to explore the different parts of her vast 

 dominions, and inquire into the communication between Asia and America. 

 Three professors of the Imperial Academy were chosen for this expedition ; Dr. 

 John George Gmelin, in the department of Natural History and Chemistry ; 

 M. Gerard Frederic Muller, as general Historiographer; and M. Louis de 

 L'Isle de la Croyere, for the department of Astronomy ; draughtsmen and other 

 proper assistants were appointed to attend them. In the summer of the year 1733 

 they departed from Petersburg ; and though a principal object of their commis- 

 sion was unavoidably neglected, from the difficulty of transporting the necessary 

 supplies of provisions to Kamchatka, yet it was the 10th year of their travels be- 

 fore the survivors returned to Europe. The thermometrical observations made 

 in the course of this memorable survey of the Russian empire were communicated 

 to the world by Professor Gmelin; and they prove in the most remarkable manner 

 the excessive rigour of the Siberian climate. It was at Yeniseisk, lat. 58^° N. 

 and long. gi Q E. of Greenwich, that M. Gmelin first observed such a descent of 

 his thermometer as we now know indicated the mercury to have been frozen. 

 This happened in the winter of 1734 and 1735. Here, says the professor, we 

 first experienced the truth of what various travellers have related, with respect to 

 the extreme cold of Siberia ; for, about the middle of December, such severe 

 weather set in, as, we are certain, had never been known in our time at Peter- 

 sburg. The air seemed as if it were frozen, with the appearance of a fog, which 

 did not suffer the smoke to ascend as it issued from the chimnies. Birds fell 



