62 
Mohs’ System of Crystallogra'phy 
the science for which it serves ; and, secondly^ With regard to its 
employment in practice. If the conceptions included under this 
system, (of class, order, genus, species), rest on the real and pure 
foundations of natural history ; if they be sufficiently applicable 
to practice, and have managed what is contained by them in a 
manner conformable to the rules of natural history ; this system 
will then be correct both in point of form and of content. If it 
possess those properties, it may differ from others, and corre- 
spond to the results of foreign sciences, or not ; it will not on that 
account lose aught of its value for the science to which it be- 
longs. In such attempts as framing this system, it is not per- 
mitted to have any thing in view but the particular object, the 
science, namely, in which one labours,— or ever to lose sight of 
its stedfast aspect, if one would not labour in vain. The small- 
est inconsistency will produce disadvantageous consequences 
that can never be remedied ; whereas the unusual and uncouth 
appearance of such a system, proceeding not from the thing it- 
self, but merely from the current opinion, will speedily disap- 
pear. But the question of most importance for estimating the 
present attempt is yet behind ; of what utility does it profess to 
be, to what is it applicable ? A natural system in general pro- 
poses two things. Firsts To enable us, with ease, to survey, in 
an unconstrained connection, the productions, of that kingdom 
which it comprehends ; and, secondly^ To put us in a condition 
to assign, by means of it, to any given production of Nature, 
possessing the requisite properties, its place in the system, in or- 
der to mark it by the denomination corresponding to that place. 
The first point will be best examined, when the system is con- 
sidered with regard to Nature itself in other words, when the 
species, genera, orders, and classes, are actually brought toge- 
ther^ care being taken that uniformity reign, so far as possible, 
through all the departments of this collocation. The second 
point depends upon the system of characters. To realise the 
former of these inquiries, the natural history system of mineralo- 
gy is itself subjoined in the first Appendix, and accompanied with 
some remarks. The system of characters will be examined 
briefly in our last section. 
2 
