[ 6 75 ] 
quickfilver : not only Mr. fEpinus ufed this method, 
but alfo Melf. Krafe, Zeicher, and Model, who fol- 
lowed Mr. iEpinus, and found it the mod conve- 
nient method. Now, in reflecting upon the proce- 
dure of other philofophers, efpecially of Melf. Muf- 
chenbroek and Reaumur, for producing artificial 
cold, by the commixtion of fnow with aquafortis, as 
the former has mentioned in his edition of the expe- 
riments of the academy of Florence, tom. i. p. 174. 
and Mr. Reaumur, in the memoirs of the academy 
of fciences of Paris for the year 1734. it is aftonilh- 
ing how it happens, that thefe learned men have not 
obtained, by a great deal, the degree of cold produced 
by the gentlemen of the academy of Peterlburg ; for 
their manner of making the experiments does not 
feem to differ much from that of Mr. Braun, as to 
what relates to any eflential circumftances, nor from 
the manner mentioned before, fo as to hinder them 
from producing effects nearly equal. Perhaps they 
may, in time, and by continued refearches, be able 
to find out the circumftances, that prevented their 
fuccefs in the experiments of thefe great men : it 
may be, becaufe the fpirit of nitre was not endowed 
with its proper quality. In fine, I muft further ob- 
ferve, that a certain degree of external cold appears 
abfolutely neceftary to the experiment. Mr. ^Epinus, 
who made it the 2§th of December, in a room where 
De Lille’s thermometer fhewed 1 2 2 degrees of cold, 
cooled the fpirit of nitre in liquifying fnow to 1 so de- 
grees, and the fnow, which they ufed, came to the 
fame degree ; in making the mixture, the relult 
was an augmentation of cold to 300 degrees. It muft 
then happen, that they had obtained the furprizing 
Vol, LI. 4 S degree 
