1816.] during the Year 1815. 59 
Chevreul, in a subsequent memoir, has shown that spermaceti, 
the crystallized matter of biliary calculi, and the adipocire of 
dead bodies, which have been all confounded together under the 
name of adipocire, are in reality three distinct bodies, possessing 
very different properties. Spermaceti, and the crystallized matter 
of biliary calculi are peculiar fatty bodies; but adipocire is a com- 
pound of various fat bodies with ammonia, potash, and lime. — 
Braconnot has shown that all oils and fat bodies may be separated 
into two substances, one solid, analogous to the margarine of Chev- 
reul; the other liquid, similar to his fluid fat. His method was to 
freeze the oil if it was liquid, and then to subject it to pressure be- 
tween the folds of blotting paper. The paper absorbs the liquid por- 
tion, while the solid portion of the oil remains behind. By plunging 
the paper into hot water the liquid oil is separated from it, and may 
be collected on the surface of the water. Chevreul has claimed 
this discovery of Braconnot as his own, asserting that he had pub- 
lished it before him. It is true that hé had shown that oils and fat 
are converted into margarine and fluid fat by the action of potash ; 
but he considered the formation of these bodies as a decomposition 
of the oil or fat; whereas Braconnot separated the two substances 
mechanically, and thereby showed that they existed united toge- 
ther, and that no decomposition was necessary in order to form 
them. 
I shall terminate my account, of chemistry by mentioning the 
resalt of Sir Humphry Davy’s experiments on the colours used by 
the ancients as pigments. ‘The red colours employed he found to 
be red lead, vermilion, and iron ochre. ‘The yellows were yellow 
ochre, in some cases mixed with chalk, in others with red lead. 
The ancients, likewise, employed orpiment ‘and massicot as yellow 
paints. The blue was a pounded glass, composed of soda, silica, lime, 
and oxide of copper. Indigo was likewise employed by the ancients, 
and they used cobalt to colour blue glass. The greens were com- 
pounds containing copper; sometimes the carbonate mixed with 
chalk ; sometimes with blue glass. {n some cases they consisted 
of the green earth of Verona. Verdigris was likewise used by the 
ancients. The purple colour, found in the baths of Titus, was an 
animal or vegetable matter combined with alumina. The blacks 
were charcoal; the browns ochres; the whites chalk or clay. 
White lead was known likewise to the ancient painters. 
VII. MINERALOGY. 
This department of science is divided into two parts; namely, 
oryclognosy and geognosy. We shall consider the improvements 
that have been made in each, during the course of the last year, 
separately. 
* I. ORYCTOGNOSY. 
I have reserved for this place the chemical analysis of such mine- 
rals, made during the course of last year, as have come to my 
