58 
Mohs’ System (^'Crystallography 
from all others. Probably the question as to the form will not 
occasion much difference of opinion. But in regard to the con- 
tent more objections may occur; perhaps from the appearance of 
the science Itself being injured by rigorously observing the rides 
(f natural history. Following the clue which botany and zoo- 
logy present, it is proper to institute some inquiry into this 
matter. 
7. Continuation . — The content of a system is determined by 
the several species it includes. The deficiency of most minera- 
logical systems appears in the erroneous settlement of the spe- 
cies ; as will easily be discovered, on comparing that settlement 
with our preceding conceptions of species (ii. 25.) ; and consi- 
dering the multifarious transitions (ii. 30.) of one species into 
another. Since the idea of species, however, is a very simple 
one in mineralogy, and the application of it any thing but dif- 
ficult ; the question occurs, whence have so many defective ar- 
rangements arisen ? 
8. Origin of this defect . — The first source of them is, doubt- 
less, to be found in the circumstance, that mineralogists have 
thought themselves obliged to admit into the system, a multi- 
tude of minerals not capable of any natural history arrangement. 
And in order to give this injudicious procedure a scientific air, 
they have next attempted to bring it under rules ; whilst, in or- 
der to render it general, without attending to the numerous ex- 
ceptions and alterations, they have applied it to other species, 
which might have followed the true principles of science. By 
this means, a multitude of species have been split asunder, al- 
though their correct arrangement would have tended to embel- 
lish the system. 
9* Explanation . — A few examples will explain this. If por- 
celain earthy green earthy &c. are to appear as independent spe- 
cies, it will be necessary to produce some basis on which those 
pretensions to independence are founded. Their form, hard- 
ness, and specific gravity, by means of whose mutual relations 
ihe independence of species in the mineral kingdom is usually 
determined, are either so difficult to measure, in the cases be- 
ibre us, or so indistinct, that no methodical distribution can rest 
'.upon them. Recourse was therefore necessarily had to colour, 
connection of the particles, the feel, the adhesion to the tongue ; 
