1817.) Chemical Classification of Minerals. 125 
under that genus to which belonged either what chemists termed its 
base, or else that substance of which it contained the greatest quan- 
tity, placing at the head of the genus that mineral, if such occurred, 
which was uncombined; and having arranged the substances in 
each of the compounds according to their quantity, placing that 
mineral next which contained the first ingredient according to the 
order of the genera in the manner words are arranged in a dic- 
tionary, calling each different combination a species. For the more 
easy arrangement of all the combinations a chemist is capable of 
producing, I found it convenient to divide the classes into orders 
distinguished by the substances included under them, being either 
binary combinations, as in the first order of combustibles, or com- 
binations of binaries with each other, as in the second order of 
combustibles, in which many of the species of the first became 
genera of the second. Thus ammonia would bea species of the 
genus nitrogen in the first order; and sulphate of ammonia, a 
species of the genus ammonia in the second order; but this plan I 
have found too complex, inconvenient, and indeed unnecessary 
among minerals; so | now throw aside the orders, or rather blend 
them together, and arrange sulphate of ammonia as it would stand 
in the second order had the orders been retained. The same method 
is followed with the other alkalies, so that they come agreeably 
together. ‘I have done the same with the other combustibles and 
with the metals: but in the class Earths I make two orders; the 
first homogeneous, containing simple minerals; the second aggre- 
gate, for the rocks. In conformity with this plan, the following 
list of all the species of minerals, as far as 1 can make them out, is 
drawn up. I would recommend the division of such species as 
carbonate of lime when there is little or no chemical difference 
among varieties of very different external characters, into sections, 
so that arragonite will be a section of the species carbonate of lime; 
every species also that occurs in as many forms should be divided 
into, 1. Crystallized: 2. Of particular shapes: and, 5. Amorphous, 
as has been in some measure done by Babington. 
This system is perfectly artificial. I should be glad to see a 
natural one, founded upon some universal and constant characters 
of easy acquirement; but as it is always necessary for the diserimi- 
nation of minerals to know their contents; and as their more ac- 
cessible characters only serve as indications of them, and are gene- 
rally comparative, it is to be feared no better foundation for a 
system will be discovered. 
List of Minerals, arranged in Classes, Genera, and Species, by 
Mr, Sowerby, with References tn Figures identifying them in 
British and Exotic Mineralogy. 
The former of these works is just completed, with figures of 
British minerals ; and I hope will be found greatly to assist the 
study of mineralogy, since figures are always more intelligible 
than the most laboured descriptions, Indeed, descriptions are so 
