356 . Mr. Wevewoon’s Method of conneéting : 
otherwife with the higher ones in which mine begins to'app a } 
and all the precautions I’ could take,’ by ufing a’ clofe muffle; 
{urrounding it as equally as poflible with’ the fuel, varying its” 
pofition with refpe&t to the draught of air, &c: proved infuf- 
ficient for fecuring the neceflary equality of heat even’ through — 
the {mall {pace concerned in thefe experiments. Nor had T. 
any idea, before the difcovery of this thermometer, of the 
extreme difficulty, not to fay impracticability, of obtaining, | 
in common fires, or in common furnaces, an uniform heat’ 
through the extent even of a few inches. | Incredible as this _ 
may appear at firft fight, whoever will follow me in the opera- 
tions I have gone through, placing accurate meafures of the 
heat in different parts of one and the fame veffel, will foon be 
convinced of its truth, and that he can no otherwife expe to 

communicate with certainty an equal heat to different pieces, 
than by ufing a fire of fuch magnitude as to exceed perhaps 
fome hundreds of times the bulk of the matters required to be 
heated. | 
To fuch large body of fire, therefore, after many Feuitlets 
attempts in fmall furnaces, not a little difcouraging by the 
irregularity of their refults, I at length had recourfe, fitting up 
for this purpofe an iron oven, ufed for the burning-on of ena- 
mel colours upon earthen ware, about four feet long, by two 
and a half wide, and three feet high, which is heated by the: 
flame of wood conduéted all round it. An iron muffle, four 
inches wide, two inches and three quarters high, and ten’ 
inches long, containing the gage and piece, was placed in the 
middle of this oven, and the vacancy between them filled up 
with earthen ware, to increafe the quantity of ignited matter, 
and thereby communicate the heat more equably from the * 
oven to the muffle. In: fuch a fituation of the muffle, in the’) 
center 
