REPORT ON MINERALOGY. 
355 
should in this respect be brought into agreement with the other 
provinces of natural history. The general analogy of natural 
history supplied one motive to this attempt, but another arose 
from the conviction that we cannot compare the chemical and 
physical characters of minerals, without first studying them inde¬ 
pendently. The chemist cannot assert that arragonite does or 
does not contain strontia, except the mineralogist can tell him 
what is or is not arragonite. 
To the execution of this very remarkable undertaking Pro¬ 
fessor Mohs brought a consummate acquaintance with the 
mineral kingdom. The plan of his task was regulated in a 
great measure by the analogy of the science of botany, in 
which system has been so successful; and the publication in 
which he first gave to the world the results of his labour w r as 
his “ Characteristic,” (Dresden, 1820,) a work of not many 
pages, but one which excited a very extraordinary interest in 
Germany. 
The “ characteristic” in any branch of natural history is a 
portion of the science distinguished from the “systematik,” in 
as much as the latter arranges individuals and species into their 
classes by a consideration of all their properties; while the 
former selects certain marks by which we may easily recognise 
in each instance the class in which any given individual has 
been placed. Thus the varieties and the species of the genus 
Lamium in Botany are placed together because of their general 
affinities ; but in the “ characteristic” of the science, the genus 
is distinguished from other flowers of similar form by a small 
tooth in the outline of the corolla on each side ; and the species 
Lamium album (White Dead-nettle), is further distinguished 
by having the tube of the calyx shorter than these teeth. 
To devise characters of this kind which should mark a series 
of successive and subordinate distinctions in the mineral king¬ 
dom, was a very curious and difficult task, and was executed 
with no small skill. We cannot here go into any detail on this 
subject; but as examples of the method we may take the cha¬ 
racteristics of the order Pyrites, the genus Copper Pyrites, and 
the species Octohedral Copper Pyrites *. 
Immediately after the publication of the “ Characteristik ” 
* X. Order Pyrites. 
Metallic. 
H 3'0 to 6*5. 
G = 4-1 to 7*7. 
If H — 4*5 and less, G is under 5*3. 
If G — 5*3 and less, colour is yellow or red. 
z 2 
V. Genus 
