Experiments upon Heat . 287 
in the refult of the experiments in queftion ; I was willing, 
however, to fee how far any confiderable alterations of fize in 
the inftrument would affe£t the experiment : I therefore pro- 
vided myfelf with another inftrument, which I ftiall call Ther- 
mometer N° 3. different from thofe already defcribed in fize, 
and a little different in its conftruCtion. 
The bulb of the thermometer was of the fame form and 
fize as in the inftruments N° 1. and N° 2. that is to fay, it was 
globular, and half an inch in diameter ; but the glafs globe, 
in the center of which it was confined, was much larger, being 
3 inches y\ lines in diameter; and the bore of the tube of the 
thermometer was much finer, and confequently its length, and 
the divifions of its fcale, were greater. The divifions were 
marked upon the tube with threads of filk of different colours 
at every tenth degree, from o° to 8o°, as in the before-men- 
tioned inftruments. The tube or cylinder belonging to the 
glafs globe was 8 lines in diameter, a little longer than the 
tube of the thermometer, and perfectly cylindrical from its 
upper end to its junction with the globe, being without any 
choak ; the thermometer being confined in the center of the 
globe by a different contrivance, which was as follows. To 
the opening of the cylinder was fitted a ftopple of dry wood, 
covered with a coat of hard varnifh, through the center or 
axis of which paffed the end of the tube of the thermometer : 
this confined the tube in the axis of the cylinder at its upper 
end. To confine it at its lower end, there was fitted to it a 
fmall fteel fpring, a little below the point o°; which, being 
confined round the tube of the thermometer, had three elaftic 
points projecting outwards, which prefiing againft the infide 
of the cylinder, confined the thermometer in its place. The 
total length of this inftrument, from the bottom of the globe 
to 
