Remarks on Alineralogical Classification. 31 
chemical perturbations that have eliminated our mountain 
masses — as fossils have told the story of past life on the 
globe, — our nomenclature must be enlarged to suit their 
new application. Without attempting to show in what 
way this revolution might be effected, I shall merely indi- 
cate how recent researches are exhibiting the defects of the 
present system. 
Certain recent investigations of Professor J. P. Cooke of 
America,* on two new compounds of zinc and antimony, go 
to show that the harmony of chemical composition and 
form, as laid down in mineralogical books, is subject to de- 
viations, which are apparently undefined laws. The two 
compounds experimented on are named respectively stihio- 
hizincyle and stihiotrizincyle ; and their chemical symbols 
are Sb,Zn^, and Sb,Zn^. The two crystalline forms which 
they assumed, were found to be constant under very wide 
variations of the per-centage of the chemical constituents 
of the crystals. Crystallizations were made, or attempted, 
of alloys differing in composition by one-half to 5 per cent., 
according to circumstances ; from the alloy containing 95 
per cent, of zinc to that containing 95 per cent, of antimony ; 
but only the two crystalline forms were obtained. 
If, thus, two beautifully crystallised products differing so 
very widely that any single analysis might lead to an en- 
tirely erroneous conclusion as to the general formula of the 
substance, the question arises, may not such variations in 
composition be quite compatible with the persistency of the 
crystalline forms found in nature ? From a variety of ex- 
amples, Professor Cooke shows that this actually prevails. 
As a consequence, the general chemical formulae of some of 
the best known mineral species, such as mica and tourma- 
line, are still uncertain. The results of these investigations 
must greatly modify our notion of a mineral species. The 
idea of this has hitherto been, — first, a definite crystalline 
form; second, a constant general formula; and any im- 
portant variation in either of these characters has been re- 
garded as equivalent to a change of species. 
Sillimaii's American Journal of Science, vol. Ixxix, 1860. 
