316 Mr. cavendish’s Ohfervations 
have happened to feveral gentlemen whofe thermometers froze 
by the natural cold of the atmofphere, and with reafon caufed 
much perplexity to fome of them. 
In this experiment the apparatus was not taken out to be 
examined till the ivory thermometer had funk to - 95 0 ; it was 
then found to be frozen folid. 
The third experiment was tried while the former was carry- 
ing on, and was made by putting the other apparatus, namely, 
that with the thermometers G and B, into the fir ft mixture 
made for the former experiment, and which may confequently 
be fuppofed to have loft great part of its cold. The ivory ther- 
mometer quickly funk to ~ 43 \ where it remained ftationary 
for near 12'. The apparatus being then taken out to be exa- 
mined, the quickfilver in the cylinder was found fluid, but 
thick and in grains, like crumbs of bread. The apparatus was 
then put back into the mixture ; and, on obferving the ther- 
mometer, it was found to have rifen to - 40°, where it re- 
mained ftationary about 4c/ ; being then examined, the quick- 
filver was found folid. 
It appears, therefore, that the cold of the mixture was fuf- 
ficient to cool the quickfilver in the cylinder about 3 0 below the ; 
point of freezing, but did not make it freeze till, on taking 
out the apparatus, the agitation fuddeuly fet it a freezing, and 
produced the appearance deferibed by Mr. hutchins. This 
immediately made the inclofed thermometer rife ; fo that when 
it was re-placed in the mixture and obferved, it flood exadbly 
at the freezing point. It appeared, by the fpirit thermometer, 
that the cold of the mixture, at the time the apparatus w r as firffc 
taken out to be examined, was only 2 0 below the point of 
freezing, which agrees very well with this explanation. 
This 
