3 T 4 An Attempt to make a Thermometer 
do. We need not be felicitous about the precife degree of 
heat employed in this baking, provided only that it does not 
exceed the loweft degree which we fhall want to mealure in 
practice ; for a piece that has buffered any inferior degrees of 
heat, anfwers as well for meafuring higher ones as a piece 
which has never been expofed to fire at all. In this part of the 
preparation of the pieces, it may be proper to inform the ope- 
latoi of a circumstance, which, though otherwife immaterial, 
might at firft difconcert him : if the heat is not in all of them 
exaaiy -equal, he will probably find, that while fome have 
begun to (brink, others are rather enlarged in their bulk ; for 
they all fwell a little juft on the approach of rednefs. As this 
is the period of the moft rapid produce of air, the extenfion 
may perhaps be owing to the air having at this moment become 
e a ic to fuch a degree, as to force the particles of the clay a 
little afunder before it obtains its own enlargement. 
VI. Each divifion of the fcale, though fo large as a tenth 
. an lnch > anfwers to T-hfth part of the breadth of the little 
piece of clay. We might go to much greater nicety, either 
by making the divifions fmaller, or the fcale longer ; but it is not 
apprehended, that any thing of this kind will be found necef- 
lary : and, indeed, in proceeding much further in either wav, 
we may poffibly meet with inconveniences fufficient to counter- 
a ance the apparent additional accuracy of meafurement. 
VII. The divifions of this fcale, like thofe of the common, 
thermometers, are unavoidably arbitrary ; but the method here 
propofed appears fufficiently commodious and eafy of execu- 
tion, t e divifions being adjufted by meafures everywhere 
nown, and at ail times obtainable : for however the inches 
ufed in different countries may differ in length, this cannot 
affect 
