11 
the Congelation cf §uh&Jifoer, 
The general hate oi M. braun’s experiments is, that with 
tlie above-mentioned frigorific mixtures, and once, when -he 
natural cold was at - 2S 0 , with rectified lpirits and fnow, he 
congealed the quickfilver, and difcovered mofl of its properties 
in a folid hate, efpecrally that it is a real metal, which melts 
with a very finall degree of heat. But not perceiving the ne- 
cefiary confequence of its great contraction in freezing, thoujrh 
aware ot the fa£t, he perpetually confounded the diminution of 
its volume from this caufe with that which is fi nly the effect 
of cold. Hence he confiderbd, as the commencement of con- 
gelation, what was, in reality, its extreme term, or the utmoh 
contraction which the whole would iuffer in becominp' folid. 
To this, indeed, he fcarcely ever attained, owing to the various 
impediments that occurred from adhefion of the quickfilver in 
the thermometrical tube, hollows left in the bulb as it froze, 
portions of the mercury remaining uncongealed, and many 
other caufes. All thefe being by their nature very irregular, his 
fuppofed freezing point came to be extremely uncertain, and 
feveral anomalous appearances were occafioned, which could 
not pofhbly be explained upon his miftaken fuppofition ; but, 
notwithstanding fuch errors, the greatefl part of our prefen t 
knowledge on the fubjea: of mercurial congelation is to be 
found in the writings of M. braun, who may therefore juflly 
be filled the father of this branch of fcience. 
In his fupplementary treatife, the Profeffor engages to con- 
tinue his refearches, and to lay the refult of them before the 
Academy, if they fnould lead to any thing new. But he did 
not live to accomplifh his defign. His original differtation avas 
re-printed, and the fupplement f rfl publifhed, in the Xlth tome 
of the Novi Commentarii Academiae Scientiarum Petropoii- 
tanae for the year 1765. This volume did not appear till 1767, 
-Vol. LXXIII. Y y and 
