227 
the compounds of chromium. 
The first of the specimens in the table analysed by me was 
from the Bare Hills, Baltimore ; its sp, gr. was 3 * 949 . Its 
constitutents differed so much from those given by Seybert 
of a specimen from the same place, that I was induced to 
repeat the analysis four times. The results did not coincide 
with each other, but all gave nearly the same ratio between 
the green oxide of chromium and the peroxide of iron. 
The second of the specimens analysed by me was from 
the Shetland Isles. Its specific gravity was 4*164 when 
purified by floating off the lightest portions, after reducing 
the mineral to powder. 
My method of analysis was this : the mineral was reduced 
to a fine powder, and heated in a silver crucible with a mix¬ 
ture of caustic potash and nitre, amounting to thrice the 
weight of the powder. I usually operated on 25 grains of 
the mineral. After keeping the mixture in a state of fusion 
for half an hour, it was raised to a red heat, and kept in that 
temperature for about ten minutes; it was then allowed to 
cool, and lixiviated in water. A fine yellow alkaline liquid 
was obtained. The undissolved portion being digested in 
muriatic acid, the whole dissolved except about ^ grain of 
brown matter, obviously consisting of ore that had escaped 
decomposition. It was deducted from the portion of ore sub¬ 
jected to analysis. 
The alkaline solution was supersaturated with acetic acid, 
and then mixed with carbonate of ammonia in slight excess. 
The alumina was thrown down. After washing and ignition 
it was dissolved in muriatic acid to separate a little silica with 
which it was mixed. 
The muriatic solution was concentrated, and then diluted 
