348 
SECOND REPORT — 1832 . 
In the same point of view, the examination of crystals formed 
from solutions is of great value to mineralogy ; as, for instance, 
the many excellent measures of artificial salts by Mr. Brooke, 
Mr. Haidinger, and others. Such crystals may often be ob¬ 
tained in much greater abundance and perfection than natural 
crystals, and especially than natural crystals of similar chemi¬ 
cal composition ; and thus they widen very much the field of 
facts to which our inquiries lead. Informer times the mineralo¬ 
gist was professedly restricted to substances which occur in 
nature; but we may venture to say that a line so arbitrary and 
accidental cannot be the true boundary of the science. Where- 
ever crystalline forces act, the crystallographer is called upon 
to pursue his speculations : these speculations, whether we 
call them mineralogical or not, are such as give interest and 
promise to our study. In this point of view mineralogy pos¬ 
sesses not only the importance which belongs to its ancient 
subjects, but also an importance of another kind, which belongs 
to it as a necessary supplement to chemistry ; for it takes into 
consideration those physical characters of chemical compounds 
(crystallization, specific gravity, hardness, fracture, lustre), 
which belong to them as solid bodies, and which indicate the 
law and intensity of the corpuscular forces by which each com¬ 
bination is bound together. The study of artificial crystals, 
therefore, whether obtained in the wet or in the dry way, may 
be recommended as very useful to the mineralogist. 
Haldat (Ann. de Chim. Jan. 1831,) has shown a mode of ob¬ 
taining artificial crystals of iron oxide by the decomposition of 
water; and these resemble the natural crystals of “ fer oli- 
giste” from Elba. So Becquerel has obtained the oxides of 
copper, lead, zinc. But by far the most valuable and im¬ 
portant of such experiments appear to be those of M. Bec¬ 
querel on the sulpliurets, iodurets, and bromurets of metals, 
which he has obtained by artificial chemical action in a per¬ 
fectly crystalline form. The agency which he employs is very 
weak galvanic tension ; and he has succeeded thus in producing 
sulphuret of silver in small octohedral crystals resembling the 
native mineral, and sulphuret of copper, also closely resembling 
the native sulphuret. The sulpliurets of zinc and iron require 
additional precautions, but are also obtained like to the native 
species; and iodurets, bromurets, and seleniurets of various 
metals are procured as crystals by similar processes. (Ann. de 
Chim. Oct. 1829.) These important steps in synthesis will 
probably throw a new light upon known analytical results. 
M. Beudant has made a number of interesting experi¬ 
ments on the subject of another class of causes which modify 
the forms of crystals, and of which the general laws are, if pos- 
