2 1 8 
Mr. Chenevix's Analysis of 
that, not only the sagacity of Nature becomes very striking; 
but, from the acknowledged accuracy of one method of investi- 
gation, the reliance to be placed upon the other is rendered more 
conspicuous ; and each receives additional strength and confir- 
mation. Chymistry has long been in the habit of aiding the 
science of mineralogy, of which it laid the foundation ; but it 
was not till lately, that crystallography could form a judgment 
of its own, much less confirm the truth of the source from 
which it sprung. 
SECTION II. 
ARSENIATES OF IRON. 
The arseniates of iron remain now to be examined. Included, 
formerly, among arseniates of copper, they have been separated 
from them, upon the authority of chymical analysis. For, al- 
though to recognize, by external character and form in all their 
modifications, substances already known, is particularly the 
province of crystallography ; yet he, who would expect that it 
should declare the nature of those substances which it beholds 
for the first time, would exact more than it ever has promised, 
or ever could perform. Among fossils, it may class, and find 
new species ; but chymical analysis is the basis of all arrange- 
ment, among metallic ores. In them, to separate, is the task 
of the one ; to assign a place, is the business of the other. 
Cupreous Arseniate of Iron. * 
One hundred parts of this arseniate, exposed to a low red 
• This species had been mentioned by Mr. Proust; but in a manner which, as 
it was a new substance, and demanded particular attention, does not give all the 
