I 
Experiments and Obfervations. 589 
which were nominated after the degree of heat fhewn at 
the fame time by the graduated thermometer. Thus, for 
inftance, a mark was put at 140°, another mark was put 
at 1 35 0 , another at 130°, and fo on. It is plain, that in 
thofe points, the thermometers when put in equal cir- 
cumftances, muft: coincide perfectly together. Now, on 
making the fcale thofe points are marked firft, and as the 
diftances between thofe marks were very fmall (confut- 
ing of a few degrees) they were divided with the com- 
paffes in the proper number of equal parts or degrees ; 
and in this manner the fcale of the other thermometer, 
was completed, by which means, although thefe two ther- 
mometers did not coincide fo well with other thermome- 
ters, yet they coincided perfectly well together, as muft 
inevitably be the cafe, even upon the fuppofition that 
their tubes were not perfectly cylindrical. The length 
of a degree on the fcale of thofe thermometers was a little 
more than ^th of an inch, and although thofe fcales were 
divided into degrees only, yet by infpetftion a perfon a little 
verfed in thefe obfervations could eafily diftinguifh the 
height of the quickfilver within a quarter of a degree. 
Thefe thermometers were both fixed upon the fame 
frame at the diftance of about one inch from one ano- 
ther, having the balls quite detached from the frame, and 
in this manner they were expofed to the Sun, or to the 
light of a lamp. 
4 I I 2, 
When 
