Reflections on some Mineralogical Systems. 4g 
and revolts against our sciences: but whatever may be its 
charms, it has no principles but our sensations; and a science 
purely descriptive is a contradiction. 
Among thousands of persons who consider the same 
thing, each will describe it according to his own ideas, and 
no one will be able to recognise it by the picture which an- 
other shall have made. But a definition is the same to all 
men; it is precise. If it totter, it is overthrown ; whereas 
descriptions are satisfied with coming near. If by the one 
we are less exposed to commit ¢rrors, because we have esta- 
blished principles ; by the other we are less in a condition to 
prove that we have been deceived, as we have followed no 
principle. 
This is not the only inconvenience of a descriptive me- 
thod. He who wishes to give a description, examines the 
object entire and in detail. He varies the aspect in a 
thousand different manners, till he believes.that he has ex- 
hausted its sensible properties. If the object be one of those 
which are susceptible of classification, and if it is a species 
which we wish to describe, this species suffers itself to be 
divided into varieties, and these varieties are composed of 
individuals whose number is almost infinite. It is there- 
fore necessary to comprehend in the description all the es- 
sential and accidental qualities of the known individuals ; 
otherwise, it would be right to refuse a place in the species 
to all those which had not this quality, or which could have 
it from others. If the description be well done,—if it be 
given in detail,—we shall have a picture which will present 
the whole of all the scattered features in divers individuals : 
but if there be some property wanting in any of these indi- 
viduals, this property excludes the species; for the species . 
cdn have neither more nor less than what is found in the 
individual. To find the true specific character then, we 
must survey all the particulars of this picture, to discard 
what belongs not in ‘common to all the individuals, for the 
rest is useless as a means of specification. We must search, 
in order not to see; and Jearn, expressly to forget. 
Let us illustrate this by example.—IJn the work of Bro- 
chant we find that the first subspecies of fluor has two co- 
lours, the second three, and the third four. What then is 
the colour of the species? If all belong to it, we might 
represent fluor by the palette of the painter. If it has only 
one, why not name it without mentioning others? If none 
properly belongs to it, why cite the colour as a specific cha- 
racter? 
Vol. 37. No. 153. Jan, 1811. D If 
