-64 Dr. 8LAGDEN* ** S Biftoty of 
was lets under Hood, M. be l’isle took the degrees of his fcale 
from decrements in the bulk of the quiekiiiver equal to ten thou* 
iandth parts of its whole volume at the heat of boiling water. 
By this method the freezing point let ms to have fallen about 
the j 5 2d degree * ; and accordingly Profdior gmelin, when- 
ever he has occalion to exprefs his obfervations in the numbers 
of Fahrenheit’s fcale, reduces them on that fuppofition. It 
is not eafy to difeover the exad time when the prefen t method 
of reckoning M. de l’isle’s degrees commenced ; but fo early 
as in M- braun’s experiments it is expreffly Hated, that the 
freezing point of his thermometer was only I 50 0 f* There 
can be no doubt, however, both from theory and from weit- 
bhecht’s Jand gmelin’s obfervations, that in the thermome- 
ters ufed during this Siberian journey, the degree at which 
water congealed was nearly as low as 15 2°; it is according to 
this proportion, therefore, that I fhall compute all Dr. gme- 
lin’s obfervations, adhering to the common rule for fuch as 
have been made fubfequent to his time with de l’isle’s ther- 
mometer. 
The next InHance of mercurial congelation to be found in 
gmelin’s journal exhibits a very Hriking example of the force 
of prejudice. It happened at Yakutfk, lat. 62° N. and long. 
130° E. in the winter of 1736 and 1737, and is thus related 
by the profeiTor §. “ This winter was unufually mild here, 
“ neverthelefs we endured at times very fevere cold, being froft- 
6t bitten in a fledge within the fpace of fix minutes, notwith- 
dt Handing all our precautions. One day, alfo, a certain per- 
* gmelin’s Reife. Theil. III. p. 143. 
t Nov. Comment. Petrop. tom, XI. p. 299* 
^ Ibid. torn. X. p. 303. 
$ Reife, Theil. II. p. 451. 
** foil. 
