the Congelation of ^tiickfher. 285 
5 lines from the top downward : when it came to melt a few 
hours afterwards, it rofe to 29 inches 7 lines, which difference 
of height was probably in part at lead: an effect of the contrac- 
tion it undergoes in freezing, its greater fpecific gravity in the 
congealed {late making it Hand proportionably lower. In the 
thermometer, part of the mercury had {luck at -44 0 ; and 
immediately under - 59 0 an empty {'pace was left, equal to 1 1 
degrees of the ficale. 'This obfervation, therefore, determines 
almofl precifely the freezing point ; for none of the quickfilver 
could have adhered in the tube fo high as -44°, unlefs it had 
congealed before it funk below this point, and confequently be- 
fore the cold exceeded this degree. And that the mercury was 
really frozen became evident afterwards ; for about eleven in 
the forenoon, as the air grew warmer, it was found to have all 
fubfided into the bulb, the fmall threads in the tube melting 
down into the vacuity left there, out of which it did not rife 
again till near two hours had elapfed. 
The accuracy of this thermometer at Irkutfk, apparent from 
its precifion with refpe£t to the point of congelation, would be 
matter of furprife, had we not been informed, that both it and 
the barometer were among the inftruments conflru£led by 
M. laxmann during his refidence in Siberia. M. georgi 
mentions them as being in the poffeffion of Dr. wachsmann, 
the public phyfician of Irkutlk, by whom probably the obfer- 
vations were communicated to the governor. 
§ 8. As the cold of America is well known to exceed that 
which prevails under the lame latitudes in Europe, we mull 
expe<ft to find quickfilver freezing fpontaneoufly in parts of that 
continent which do not lie very far to the northward. Ac- 
cordingly, befides the in {lance of Quebec formerly mentioned, 
E e e 2 * ’ this 
