Experiments upon Heat . zgi 
It having been my intention from the beginning to examine 
the conducing powers of the artificial airs or gaffes, the 
thermometer 
farther knowledge of the nature of heat, to afeertaln, by indifputable evidence, 
its paifage through the Torricellian vacuum, and to determine, with as much 
precision as pofiible, the law of its motions in that medium ; and being appre- 
henfive that doubts might arife with refpedt to the experiments before defcribed, 
on account of the contact of the tubes of the inclofed thermometers in the 
inflruments made ufe of with the containing glafs globes, or rather with their 
cylinders ; by which means it .might be fufpefted, that a certain quantity, if not 
all the heat acquired, might poffibly be communicated : to put this matter 
beyond all doubt, I made the following experiment. 
In the middle of a glafs body, of a pear-like form, about 8 inches long, and 
2 1 inches in its greateft diameter, I fufpended a fmall mercurial thermometer, 5J 
inches long, by a line thread of filk, in fuch a manner that neither the bulb of 
the thermometer, nor its tube, touched the containing glafs body in any part* 
The tube of the thermometer was graduated, and marked with fine threads of filk 
of different colours bound round it., as in the thermometers belonging to the 
other inftruments already defcribed ; and the thermometer was fufpended in its 
place by means of a fmall Heel fpring, to which the end of the thread of filk 
which held the thermometer being attached, it (the fpring) was forced into a 
fmall globular protuberance or cavity, blown in the upper extremity of the glafs 
body, about half an inch in diameter, where the fpring remaining, the thermo- 
meter neceflarily remained fufpended in the axis of the glafs body. There was 
an opening at the bottom of the glafs body, .through which the thermometer was 
introduced.; and a barometrical tube being foldered to this opening, the infide of 
the glafs body was voided of air by means of mercury; and this opening being 
afterwards fealed hermetically, and the barometrical tube being taken away, the 
thermometer was left fufpended in a Torricellian vacuum. 
In this.mftrument, as the inclofed thermometer did not touch the containing 
glafs body in any part, on the contrary, being diftant from its internal furface an 
inch or more in every part, it is clear, that whatever heat palled into or out of the 
thermometer mull have palled through the furrounding Torricellian vacuum: for 
it cannot be fuppofed, that the fine thread of filk, by which the thermometer 
was fufpended, was capable of conducing any heat at all, or at leafi: any fenfible 
quantity. I therefore flattered myfelf with hopes of being able, with the 
Q -9 a alfifiartcs 
S5' 
