cf Magnefia Earth. 465 . 
Magnefia, fays M. Bergman, expofed to a 
long continued, and very violent fire, aggluti¬ 
nates and begins to fhew figns of fufion, efpe- 
cially if the Magnefia has been prepared, by 
calcination, from the mother leys. Mon. Dar- 
cet, on the contrary, had averred, that the earthy 
t>afis of Epfom Salt refitted the a&ion of a fire 
equal, in continuance and force to that of a 
Porcelain furnace. And M. Macquer, in the 
new edition of his Chemical Dictionary, declares, 
that he has expofed the Earth of this Salt to 
the greateft heat, that could be formed in the 
focus of M. de Trudaine’s large lens, without 
the leatt appearance of a tendency to fufion. 
M. Morveau had operated on Magnefia fepa- 
rated from the mother ley of Nitre, and had 
concluded it to be, not only in itlelf, the molt 
fufible of all earths, but that it even decided the 
fufion of other earths. • But on making his expe¬ 
riments with Magnefia, precipitated from Epfom 
Salt, he found, that on leparately expofing two 
Ueffian crucibles, the one containing Chalk, and 
the other an equal portion of Magnefia, to the 
ftrongeft degree of heat, that could be produced 
in M. Maequer’s furnace, the chalk was fufed into 
a beautiful tranfparent glafs, and had attacked 
and dilfolved the crucible, for more than half 
its thicknefs, wherever the Calcareous Earth had 
reached. But the Magnefia was formed into 
a round, white, opake, folid, mafs, not having 
the appearance even of the femivitrification of 
Vol. I. H h Porcelain, 
