' Corundum Stone from Asia. 4 2 5 
appropriate terms to all the characters which occur, and which 
the senses can discriminate. In 1774, °P ene d his system of 
external characters of minerals, and the perfection he has since 
given to it, has rendered it very general. The Leskean collec- 
tion, arranged after Mr. Werner’s method, has procured, in Mr. 
Kirwan, a powerful support to the introduction of that system 
in this country ; and we have already some other valuable pub- 
lications, to recommend and introduce other favourite systems 
of the Continent. It is, therefore, at this time the English 
mineralogist should be invited to examine, if not to prefer, per- 
manent characters, so far as the progress of crystallography has 
collected them, or at least to give them a distinguished rank 
among external characters of bodies. 
If prejudice too long has retarded the union of intrinsic and 
extrinsic characters, it has also occasioned a schism among 
the advocates of crystallography. 
Rome' de l’Isle, in the year 1772, published the first edi- 
tion of his Essay on Crystallography, which he states to be a 
supplement to Linnaeus ; and, by the assistance of a very few 
friends, fie was enabled to increase the number of crystals in 
a degree to assume the appearance of a system. He fold me, 
that the accuracy of his measurement of angles of minute crys-^ 
tals was the acquirement of great practice, but that the Count 
de Bournon, after a short practice, attained equal correctness, 
and afforded him assistance, which he acknowledges in his 2d 
edition to have received, particularly by the discovery of crys-* 
tals in Dauphine, Auvergne, Franche-Comt4, &c. 
The Abb6 Hauy, an accurate and patient observer, and a 
good mathematician, considered crystallography as founded on 
certain laws, reducible to demonstration by calculation. In the 
MDCCXCVIII. 3 I 
