341 
and Alineralogy^ 
example, the denomination merely signifies, that the form of the 
species belongs to the rhomboidal system, and that the cleavages, 
on the other hand, takes place according to prisms, which (I. 
can be no other than regular six-sided prisms. In the second 
example, the denomination indicates, that the forms belong to 
the pyramidal system, and that the cleavage takes place accord- 
ing to prisms, which must, therefore, (I. 44.) be rectangular 
four-sided prisms. When the system of crystallizations and the 
cleavages of two or more species agree, as in several calcareous 
haloids, augite-spars, and others, a particular property of the 
crystallizations, &e. is chosen to form the special denomina- 
tion ; such as long or short-axed^ right or oblique angled, and 
so on. The term axifrangible or axis-cleaving, denotes a par- 
ticular direction of cleavage perpendicular to the axis, as in axi- 
frangible zeolite ; pidsmatoidal denotes one particular direction 
of cleavage, parallel to the axis, as in prismatoidal antimony- 
glance, Few adjectives have been borrowed from colours, coun- 
tries, and other such peculiarities ; and “ common^'' the worst 
of all epithets, though it abounds in German writings, has not 
been used at all. 
18. How the Systematic Nomenclature is to be judged of.’— 
A systematic nomenclature must be estimated solely by the sys- 
tem from which it is deduced. If that system is founded on re- 
lations which constitute an object of the science under conside- 
ration ; if it is consistent with those principles, and possesses, 
besides, the other requisite qualities, in that case, the duty of a 
nomenclature extends no farther than faithfully to represent 
that system by denominations. If it accomplish this, — if it be 
conformable to the usual modes of speech,— -if it reject unneces- 
sary innovations, and at the same time introduce a description 
of the object into each of its denominations, — it will then have 
fulfilled its chief obligations, and may quietly entrust its im- 
provement and refinement to the diligence and reflection of fu- 
ture times. 
19. Trivial Nomenclature not to be throwir away, — It cannot 
be called a hurtful practice to give the productions of Nature, 
particularly those which frequently come under our manage- 
ment, lor other purposes than those of science, such names as 
