REPORT ON MINERALOGY. 
plification rests between them ; and all must allow the propriety 
with which Prof. Naumann of Freiberg, the author of the best 
recent system of Crystallography, has dedicated his work “ to 
Mohs and Weiss, the Coryphaei of German erystallographers.” 
The distinction of systems is now generally adopted. Thus 
Germar, (1830,) one of the most recent authors, has the tessular, 
pyramidal, prismatic, and hexagonal systems, each subdivided 
into homohedral and hemihedral, as all or half the faces occur ; 
—the oblique prisms are considered as hemihedral and tetarto- 
hedral right prisms, according to the method of Mohs, whose 
notation also is retained. In England, the distinction of sy¬ 
stems of crystallization has not been explained, so far as I am 
aware, except in Mr. Haidinger’s translation of Mohs. 
Crystallography is essentially a mathematical subject. The 
striking mixture of simplicity and complexity which here, as in 
other parts of nature,—but yet more here than in any other part 
of nature,—offers itself to our notice, depends upon the com¬ 
bination of the primary forms belonging to the above systems 
with the geometrical and numerical laws by which other forms 
are derived from these. To trace the properties of such derived 
forms, and of their combinations, necessarily requires some 
considerable portion of mathematical calculation, which may 
however be of several kinds. Spherical trigonometry, solid 
geometry, and analytical geometry of three dimensions, may 
any of them be made to answer the purposes of the crystallo- 
grapher. Haiiy and Mohs, proceeding in the manner which, of 
the three, implied the least extended acquaintance with mathe¬ 
matics, employed in most instances particular constructions and 
calculations founded on solid geometry, and though they thus 
want the conciseness, beauty, and generality of other methods, 
they are perhaps, in consequence of this, intelligible to a wider 
circle of students. Monteiro, Bournon, Cordier, Soret, and 
others, have followed the method of Haiiy; and denominations and 
notations borrowed from it are still common in our catalogues. 
Phillips also, so far as he referred to any method, employed that 
of Haiiy ; but his extraordinary merits consisted rather in de¬ 
termining the angles and forms of individual specimens and 
species, than in referring them to any general law. 
Prof. Hausmann of Gottingen, a pupil of Mohs*, has laboured 
* Referring to this account, Professor Hausmann has made the following 
statement in the Land, and Edinb. Philosophical Magazine for August 183d : 
“ Already in 1803, and therefore earlier than Mohs, I became a mineralogical 
writer, building my system on peculiar views belonging to no other school. I 
was the first who appeared as opponent to Werner, assisted in the spreading of 
Haiiy’s theory, and published my first mineralogical system in 1809, founded 
on chemical composition and external characters.” I beg to apologise, there¬ 
fore, for an error occasioned by haste and the want of books. 
