for meaf uring the higher Degrees cf Heat , See. 31 5 
affect the accuracy of the fcale, provided that the proportions 
between the wider and narrower end ol the gage are exactly as 
five-tenths of thofe inches to three-tenths, and the length 240 
of the fame tenths ; and that the pieces in their perfectly dry 
hate, before firing, fit precifely to the wider end. When one 
gage is accurately adjufted to thefe proportional measures, two 
pieces of brafs fhould be made, one fitting exactly into one 
end, and the other into the other : thefe will ferve as ftandards 
for the ready adjuftment of other gages to the dimenfions of 
the original. 
By this Ample method we may be allured, that thermome- 
ters on this principle, though made by different perfons, and 
in different countries, will all be equally attested by equal de- 
grees of heat, and all fpeak the fame language : the utility of 
this laft circumftance is now too well known to need being 
in filled on. 
VIII. If a fcale two feet in length fhould be reckoned incon- 
venient, it may be divided into two, of one foot each, by 
having three pieces of brafs fixed upon the fame plate ; the 
firft and fecond, five-tenths of an inch apart at one end, and 
four-tenths at the other ; the fecond and third, four-tenths at 
one end, and three-tenths at the other ; fo that the firft reaches 
to the 1 20th divifion, and the fecond from thence to the 
240 th. 
IX. As this thermometer, like all others, can exprefs only 
the heat felt by itfelf, the operator muft be careful to expofe 
the pieces to an equal action of the fire with the body 
whofe heat he wants to meafure by them. In kilns, ovens, 
reverberatories, under a muffle, and wherever the heat is 
pretty fteady and uniform, the means of doing this are too 
T t 2 obvious 
