the Congelation of Quickfiiver. 
any other rather than the real caufe, though they are now 
found to carry with them a force of internal evidence which 
cftablifties the truth beyond all doubt. 
Jn enumerating thcfe fafh, I (hall continue to pur Ate a chro- 
nological order. They are in general of fuch a kind as could 
fcarcely become an object of attention,, till thermometers had 
acquired feme degree of accuracy. This did not happen till 
near the year 1730, and the fir ft obfervations which prove the 
freezing of quickfilver were made within four or five years of 
that period: fo intimately are improvements in philofophy 
connedted with the perfection of inftruments ! 
§ 1. When the Emprefs anna iwanovna had afe ended the 
throne of Ruflia, fhe refolved to carry into execution one of 
the favourite ideas of her illuftrious uncle, peter the Great, 
by fending out proper perfons to explore and deferibe the dif- 
ferent parts of her vaft dominions, and enquire into the com- 
munication between Alia and America. Three pro feffors of the 
Imperial Academy were chofen for this expedition ; Dr. john 
george gmelin, in the department of Natural Hiftory and 
Chemiftry; M. gerard Frederic muller, as general Hifto- 
riographer; and M. louts de l’isle de la croyere, for the 
department of Aftronomy; draughtfmen and other proper 
affiftants were appointed to attend them. I11 the fummer of the 
year 1733 they departed from Peterfburg ; and though a prin- 
cipal objeT of their commiffion was unavoidably negle&ed, 
from the difficulty of tranfporting the neceflary fupplies of 
provifions to Kamchatka, yet it was the tenth year of their 
travels before the furvivors returned to Europe. 
The thermometrical obfervations made in the courfe of this 
memorable furvey of the Ruffian empire were communicated 
B b b 2 to 
