[ 221 ] 
et below melting ice, by which any given tempe- 
rature is expreffed, will be as the value of each de- 
gree inverfely ; that is, if each be a given part of 
the fundamental interval, as the value of the fun- 
damental interval inverfely j but, if the degrees of 
different fcales be different parts of the fundamental 
intervals, as the value of the fundamental interval 
inverfely, and the number of degrees contained in 
it diredly.. 
It is ncceffary here to explain fome qf my ex- 
preffions. By the fundamental interval is to be un- 
derftood the whole extent of the fcale between 
melting ice and boiling water. This is not a 
particular length ; for its length is not the fame, even 
in thermometers made in the fame date of the ba- 
rometer, unlefs their figures be equal and fimilar 
hut it is a portion of the whole folid content of the 
thermometer, including fo much of the tube, as 
reaches up to the point of melting ice ; and it is the 
fame portion of the whole folid content in all made 
in the fame flate of the barometer ; but in fuch as 
have been made in different dates, a different por- 
tion in each. The degrees of the fcale are fub- 
divifions of this portion of folid content, into leffer 
aliquot parts. With refped to the number of thefe. 
fubdivifions, the pradice of different countries is 
different. By the value of the fundamental inter- 
val, or of the degrees of a thermometer, I mean 
the fradions, which exprefs what parts they are 
refpedively of the whole folid content, terminated 
as above that is, by the point of melting ice : and 
by the proportion of the fundamental intervals,, or 
of the degrees, of different indruments, compared 
together, I. underdand the proportion of thefe frac- 
tions, . 
