57 
and Mineralogy. 
Earthy Minerals, natural history families are combined along 
with those genera. Whoever is accustomed to use a system, 
will be as much astonished at those double genera, as at the to- 
tal want of genera in some classes or orders of many systems. 
4. Continuation. — Mineralogists have seldom been contented 
with the steps of classification, used in other departments of na- 
tural history. They have at one time rejected, at another ap- 
pended, whatever seemed convenient. Perhaps this practice 
might be founded on satisfactory reasons ; but if those reasons 
apply to one portion of a system, they likewise apply to all the 
rest, otherwise the system would be incongruous, that is to say, 
have no regular form. But regularity of form is absolutely in- 
separable from the idea of a system. And hence, if one class 
contain orders and genera, the others must contain them like- 
wise, and so in other points. If we set out from right princi- 
ples, — ^in natural history, from natural history principles, — this 
object is attained without difficulty or obstruction ; but if in na- 
tural history, we set out from chemical principles, or in chemi- 
stry from natural history principles, it cannot be attained with- 
out constraint. 
5. The Natural History System is free from these faults.^ 
Whatever may be thought of the natural history system, it is not 
surely chargeable with any defect in point of form. It contains 
the two essential conceptions, genus and species, both settled 
upon one principle. It also contains classes and orders ; thus 
conforming itself in its steps of classification to the general cu- 
stom of natural history. In zoology and botany, a genus or an 
order is occasionally so extensive, that the inspection of it re- 
quires to be facilitated by a new subdivision. It is quite evi- 
dent, that subdivisions of this kind do not belong to the essence 
of form. Mineralogy does not need them. The natural history 
system of mineralogy is likewise uniform throughout ; in other 
words, it maintains through all its parts the same steps of classi- 
fication ; and these are everywhere of equal value, — a circum- 
stance which does not happen universally in other systems of 
mineralogy. 
6. Defect of the content. — As form is an essential part of eve- 
ry system, so the content of that system is not less essential. 
And here the natural history system is more or less distinguished 
