on Mr. iiutchin .’s Experiments 3 fj 
I have formerly kept a thermometer in melted tin and lead 
till they became folid ; the thermometer remained perfectly 
.ftationarv from the time the metal began to harden round the 
hides of the pot till it was intirely folid ; but I could not per- 
ceive it to finjc at all below that point, and rife up to it when 
the metal began t© harden. It is not unlikely, however, that 
the great difference of heat between the air and melted metal 
might prevent this effecf from taking place ; fo that though I 
did not perceive it in thofe expriments, it is not unlikely that 
thole metals, as well as water and quickfilver, may bear being 
cooled a little below the freezing or hardening point (tor tpe 
hardening of melted metals and freezing of water teems exactly 
the fame proceis) without beginning to lofe tnen fluidity. 
Mr. iiutciiins’s five fir, ft experiments were made with the 
apparatus, and m the manner above oeicnbed. In the iirft ex- 
periment the ivory thermometer, inclofcd m the cvhndci, 
funk to - 40°, where it remained ftationary for about half an 
hour, though the wooden thermometer, placed in the fame 
mixture, kept finking almoft all the while. At the end ot that 
time the apparatus was. taken out ot the mixture to be examined, 
and the quickfilver in the cylinder was found frozen. It fee ms 
evident, therefore, that the true point at which mercuiy fieezcs 
is 40° below nothing on the thermometer F, which was that 
made ufe of in the experiment. It cannot be lower than that, 
their containing more or lefs of a fubftance called the matter ot heat ; and as I 
think Sir isaac newton’s opinion, that heat con lifts in the internal motion of 
the particles of bodies, much the moft probable, I chofe to ufe the expreffion, heat 
is generated. Mr. Wilke alfo, in the Tranfaclions of the Stockholm Academy 
•of Sciences, explains the phenomena in the fame way, and makes ufe of an hypo- 
thefts nearly ftmilar to that of Dr. black. Dr. black, as I have been informed, 
makes the cold produced by the thawing of fnow 140°; Mr. wilke, 130 . 
T t 2 ' ‘ ‘ for 
