194 Chemical Classification of Minerals. [Fes. 
About a mile and a half further west along this shore, near Rascaril, 
we found in the old red sand-stone a bed of sandy lime-stone 40 
feet thick, and traceable for nearly twice that distance, and there 
is in this formation, half a mile from the junction | before described, 
evident indications of coal. It crops out in different places, but 
the trials for working it that have been hitherto made have not 
been attended with success. 
On the road from Balearry to Castle Douglas, near Orchardton, 
we fall in with the granite for a short way, but soon again meet the 
transition country, which extends all along the valley of the Ken. 
Article VIII. 
Chemical Classification of Minerals. By Mr. Sowerby, F.L.S. 
: (To Dr, Thomson.) 
_ SIR, 
Tue recent appearance of an introductory publication on 
mineralogy, in which the minerals are arranged in an order de- 
pendant on their contents, induces me to forward to you for publi- 
cation a sketch of a system * adopted many years ago, because it 
does not appear to be generally known, I would recommend it in 
preference to other artificial systems, because it contains a fixed 
rule for the arrangement of every substance when its nature is 
known; and it is capable of modification with facility as fast as the 
science of chemistry advances. Some changes have been lately 
made, and others may be introduced; but I prefer laying it before 
the public in its present form, rather than have to make frequent 
alterations, which might be the case were I to adopt too suddenly 
all the changes chemistry has of late undergone. I shall be happy 
to receive suggestions of any kind by which it may be improved, as 
also any additiun to the list of minerals accompanying the sketch. 
As soon as, from various considerations, I had determined to 
arrange minerals from their analysis, 1 sought for some property or 
character, which, like the fructification of plants, should be pos- 
sessed by every substance that enters into their composition, and 
according to the modifications of which such substance might be 
disposed, as a basis for the arrangement of minerals. The specific 
gravity of the elements fully answered my wishes, whereupon 1 
divided these elements into three classes: 1. Combustibles: 
2. Earths: 3. Metals, placing the lightest class first, then the 
lightest individual at the head of the class, and proceed to the 
heaviest, calling each a genus: every compound was next placed 
* Published in my Catalogue of British Minerals in 1811, and in my British 
Mineralogy, with figures, periodically. 
