the Congelation oj ^uickfilver. 
'man may have {Length enough to {hake it off. Were we fure 
that philofophy would continue to be regularly cultivated, per- 
haps it might with truth be affirmed, that the utmoft efforts of 
genius amount only to a power of anticipating difcoveries which 
would neceffarily be made in the courfe of a few years by the 
common prog-refs of mankind. The principles of this experi- 
ment for determining the point of congelation in mercury 
being already before the world, it was moft probable, that the 
confequences to be deduced from them would not efcape gentle- 
men of fuch acknowledged fagacity, whenever they might 
happen to apply their attention to that fubject. 
Though the methods propofed by Mr. cavendish and Dr. 
elack were fundamentally the fame, yet there was fome dif- 
ference in the apparatus they recommended ; and as the former 
gentleman got his executed in London and fent out to Hudfon’s 
Bay, it was that which Mr. hut-chins employed in, performing 
moft of his experiments. A circumflantial detail of thefe has 
fo recently been read before the Society, that it would be tedious 
for me here to recapitulate the particulars. They have not only 
confirmed the preceding obfervations relative to the folid ftatc 
into which quickfilver can be brought by cold, its metalline 
fplendor and poliffi when fmooth, its roughnefs and crydalliza- 
tion where the fur face was unconfined, its malleabillity, foft- 
nefs, and dull found when (truck ; but have alfo clearly demon- 
ftrated, that its point of congelation is no lower than - 40°, 
or rather -39°, of Fahrenheit’s Icale ; that it will bear-, 
however, to be cooled a few degrees below that point, to which 
it jumps up again on beginning to congeal; and that its rapid de- 
fcent in a thermometer through many hundreds of degrees, 
when it has once pad the above-mentioned limits, proceeds 
•merely from its great contra&ion in the adt of freezing. Thefe 
Z z 2 and 
