MINERALOGY. 
found mixed with small particles of quartz, 
scarcely to be perceived by the eye. The 
trapp is also sometimes mixed with very 
tine particles of feltspar, or of calcareous 
spar, &c. After this experiment, the hard- 
ness of the stone in question must be tried 
with steel. The flint and garnets are com- 
monly known to strike fire with steel; but 
there are also other stones, wliich, though 
very seldom, are found so hard as likewise 
to strike fire. There is a kind of trapp of 
that hardness, in which no particles of felt- 
spar are to be seen. Coloured glasses re- 
semble true gems; but as they are very 
soft in proportion to these, they are easily 
discovered by means of the file. The com- 
mon quartz-crystals are harder than colour- 
ed glasses, but softer than the gems. The 
loadstone discovers the presence of iron, 
when it is not mixed in too small a quan- 
tity in the stone, and often before the stone 
k roasted. Some kinds of haematites, and 
particularly the cerulean, greatly resemble 
some other iron ores; but this distinguishes 
itself from them by a red colour when 
pounded, the others giving a blackish pow- 
der, and so forth. 
In a work of this magnitude we cannot 
enter much at large into historical details ; 
it may, however, be proper to notice in 
brief the principal different systems that 
have been given to the world. 
The system of Cronstedts w-as publislied 
in 1758, and for twenty years was generally 
received by the scientific world. In 1780, 
a translation of Cronstedt’s mineral system 
appeared in Germany, accompanied with 
notes, by Werner, the Professor of Minera- 
logy at Freyberg in Saxony. Six years be- 
fore, the professor had published a separate 
treatise on the classification of minerals, in 
which he exhibited much skill in a method of 
describing them by means of external charac- 
ters.IFerper’s method is chiefly, ifnot wholly, 
followed in Germany, and is highly regard- 
ed in this and other countries. This system 
was introduced here by Mr. Kirwan, in 1784, 
who further elucidated it some years after- 
wards by a new and much enlarged edition 
of his work. In preparing the latter edi- 
tion, Mr. Kirwan had the advantage of con- 
sulting one of the completest and best ar- 
ranged collections of minerals which had 
been made in any country. This vvas col- 
lected by Leske, and after him is called the 
Leskean collection. It was arranged be- 
tween the years 1782-1787, according to 
the principles of Werner, and with his assis- 
tance. After the death of Leske, a cata- 
logue of it was drawn up, wiiich is divided 
into five parts : the first, which is denomi- 
nated the characteristic parts, consists of 
specimens intended for the illustration of 
the external characters of the classification. 
The second, which is the systematic ororyc- 
tognostic part, comprehends all simple mi- 
nerals distributed according to their genera 
and species, agreeably to the method at 
that time followed by Werner. The next 
is the geognostic geological part, which in- 
cludes the substances found in the different 
kinds of rocks, as they are divided into pri- 
mitive, transition, stratiform, alluvial, and 
volcanic mountain. This part of the col- 
lection is very rich in petrifactions. The 
fourth part is intended to illustrate the mi- 
neralogy of every country on the globe, by 
exhibiting its mineral productions. The 
fifth part is called the economical collec- 
tion, and is formed of specimens which are 
employed in arts and manufactures, as in 
architecture, sculpture, agriculture, jewel- 
ry, dying, clothing, pottery, glazing, en- 
amelling, polishing of metals, furnape-build- 
ing, medicine, metallurgy, &c. This short 
account of a very valuable collection may 
be a guide to collectors and amateurs in the 
science. In France, the mineralogical 
treatises of Brochant, Hauy, and Broug- 
niart may be noticed ; these have already 
been referred to in the course of our vo- 
lumes, but claim a distinct enumeration 
here. The system of Brochant is formed 
on the principles of Werner’s classification, 
and is thought to be the most perspicuous 
account of the German mineralogy that has 
yet been published. The system of Hauy 
divides itself into four classes. The first 
class consists of substances which are com- 
posed of an acid united to an earth and al- 
kali, and sometimes to both. The second 
class includes only earth substances, but 
sometimes combined with an alkali : it con- 
stitutes the silicious genus of other sys- 
tems. The third class comprehends com- 
bustible substances which are not me- 
tals. The metals form the fourth class. 
This is divided into three orders, which are 
characterized by different degrees of oxy- 
dation. Besides these cla.sses, there are 
three appendices. The first contains those 
substances, the nature of vvhich is not suffi- 
ciently known to have their places accu- 
rately assigned in the system. The second 
appendix includes aggregates of different 
mineral substances: and the third is de- 
voted to the consideration of volcanic pro- 
ducts. 
