„ 5 g Mr. Wedgwood’s Analyfis of a 
the ufual modes of application, 1 prefame, it cannot be confi- 
c’cred as a combination of any ot thole earths 01 calces with 
any 0 f the known acids; for all the combinations of this kind 
would, in one or other of the above methods of trial, have 
had the earth or metal difengaged from the acid. 
Whether this fubftance belongs to the earthy or metallic clafs, 
I cannot abfolutely determine ; but am inclined to refer it to 
the earthy; becaule, though brought into perteft tuhon, m 
contact with inflammable matter, and in dole vtflds, it does 
not aflume the appearance which metallic bodies do in that 
circumftance. 
Examination of the black particles . 
Thefe particles, which bore but a very fmall proportion to 
the other matter, were in form of Alining black leaks, very 
thin, and very light. One grain weight of them, carefully 
picked out, expofed to a fire which was gradually railed to 
about 90°, and continued in all about 40 hours, 111 a veflel 
loolely covered, was almoft wholly diffipated, and what little 
remained was perfectly white. Marine acid had no effect on 
It. 
Fifteen grains of the entire mineral loft, in the fame fire, 
three grains. After ieparating from another portion of the 
mineral, by waffling and otherwife, a confiderable quantity of 
the white matter, 1 5 grains of the remainder, containing of 
courfe more than its due proportion of the black,, loft five grains ; 
fo that it feems principally to be the fubftance 011 which the 
blacknefs depends that is deftroyed or diffipated by fire. The 
fame quantity, 1 5 grains, of common black-lead loft in the fame 
fire above 14 grains, the refiduum weighing lei's than one grain. 
Though 
