the Congelation of ®uickf,lver. „„ 
tubes of a large bore; with which laft he remarked, that die 
quickfdver m them fell fenfibly on freezing, and aflumed a 
concave lutface ; hkewiie, that the congealed pieces would fink 
m fluid mercury ; all evident proofs of its great contrition. 
I hefe obfervations were frequently repeated during the winter 
with iome variety in the circumftances and phenomena, by 
Profeflor Braun and many other perfons ; I fi n( j yj 
Lomonosov, Profeflor of Chemiftry, the Apothecary-general 
MODEL, Mefl. KRASE, IIIMSEL, and poissonnier, quoted on 
different occafions as witneffes, they having all either performed 
or aflifted at the experiments. Such evidence one would have 
imagined diffident to place the faff beyond all con troverfy, and 
render the congelation of mercury one of the moft acknow- 
ledged truths in natural philofophy. 
It may not here be improper to remark, as an additional' 
proof how much we are indebted to accident for difeoveries, 
that it. Mr. braun had chanced to begin with a fpirit thermo- 
meter inflead of a mercurial one, we might very pofhbly to 
this day have remained ignorant that quickhlver would freeze. 
For fince, to judge from Mr. Hutchins’s experiments, the for- 
mer would have funk but a few degrees in the frigorific mix- 
ture, it is not improbable, that the profeffor, difeouraged by 
luch a failure of fuccefs in the immediate obje# of hispurfuit, 
would have relinquithed all further attempts of this nature. 
When the fealon for experiments requiring cold was part, 
Profeffor braun employed himfelf in drawing up a general ac- 
count of fuch as he had then made, which he communicated 
to the Peterfourg Academy on the 6 th of September, i 760, 
O. S. and printed foon afterwards as a feparate differtation* 
Of this fo copious an extra#, by Dr. watson, is already in- 
* Ee admirandq frigore arciflciali dilfertatio. 
ferted. 
