and of a Mmeralogi(M System^ hy the late Dr Walker. 9S 
It fe now sufficiently evinced, that the numerous minerals in 
the globe cannot be investigated, discovered and ascertained, by 
either of these; two methods, independent of the other. This 
leading principle was the maxim of the two best judges I have 
ever known. Dr Cullen and the Earl of Bute, whose opinions 
and instructions on the subject I always found judicious and 
useful. 
An arrangement of minerals, founded merely on their natural 
characters, has been often attempted, but has always been found 
unavailing and useless. On the other hand, a method strictly 
chemical, as that of Bergman, exclusive of all natural charac- 
ters, though necessary and useful in the science of chemistry, is 
utterly incapable of discriminating the numerous minerals in na- 
ture. 
The most useful system of minerals must therefore be a mix- 
ed method, founded on their natural and chemical qualities com- 
bined,— the chemical properties to form generally the leading 
character of the classes and orders ; and the natural properties, 
the subordinate and distinctivexharacter of the genera and spe-» 
cies,— a method, if properly executed, equally useful to the 
naturalist and the chemist. 
Upon this principle, a Schediasma FossUium^ or a general 
enumeration of minerals, according to their classes,, orders and 
genera, was printed in the year 1782. Afterwards, in a larger 
treatise, entitled. Classes Fossilinm^ printed in the year 1787 ; 
•the natural and chemical character of each class, and of each or- 
der, was delivered at length. A more extensive work on the 
subject still remains in manuscript, which I have hitherto only 
exhibited to the students attending my lectures.- It contains the 
natural and chemical character of each genus of minerals, accom- 
panied with the synonyms of authors, and incidental observa^ 
tions. 
After a careful survey of all the systems of minerals that have 
been formed, I was convinced that they are all too confined i® 
the number of members or divisions, of which they are com- 
posed. The minerals now known are already too numerous to 
be arranged with perspicuity, under any small number of classes 
and genera ; and the number of known minerals is certainly 
small, compared with- what probably will be brought to light. 
