-94} Dr Walker's Miner alogical System. 
It appeared, therefore, necessary, even at present, to enlarge 
considerably the number of divisions in the mineral system. 
In the catalogue, minerals are distributed into classes, 
orders, genera, species and varieties. This fivefold [division, 
though arbitrary, is excellent ; and has now, from experience, 
been found the best in the arrangement of natural bodies. It is 
even applicable and commodious in other departments of science. 
Dr Cullen thought that no other should be followed in minera- 
logy ; and he accurately observed it himself, in his nosology, in 
the arrangement of diseases. He certainly did much in ascer- 
taining the classes, orders and genera of diseases ; but always re- 
gretted, that neither his opportunities nor his life were sufficient 
to ascertain the species. The same complaint may be applied 
to mineralogy. The classes, orders and genera, may be defined ; 
but to determine the species is difficult. It is a difficulty, how- 
ever, which, to a great degree, may be obviated or removed. 
In consequence of these ideas, the method of minerals which 
I constructed, previous to the year 1787, comprised 19 classes, 
67 orders, and 323 genera; a greater number of divisions than 
had yet appeared in any mineralogical system. These genera 
comprehended all the minerals I had collected, all that I had 
ever seen in numerous collections, and all that I had found suf- 
ficiently described by mineralogical writers. This number of 
genera, I believe, cannot well be much lessened, but must ne- 
cessarily be enlarged by future discoveries. Since the year 
1787, it has been requisite to add to this number 10 new ge- 
nera. 
The catalogue of ’my collection contains 1569 species and va- 
rieties of minerals, arranged under the above genera ; but of these 
there are so many duplicates and varieties of less note, that the 
number of specimens may probably amount to above 3138. 
These, however, do not form the whole of my collection. They 
are extracted from the general register of my museum, which 
contains many minerals, that, for want of examination, could not 
be inserted in their proper places in the catalogue. 
N. B. This MS. was written several years before Dr Walker 
ceased to lecture, and before he had adopted views still more 
agreeable to the Natural History Method *. 
• The collection, we understand, will soon be arranged for public sale by the 
Trustees of Dr Walker.— -E d, 
