in regard to Discoveries in Crystallography. £7T 
of crystals, consist of, or are contained under, faces all equal and 
similar to each other ; and that those faces which arise from 
truncations, acuminations, and bevelments, lead to similar forms, 
if the homologous planes are duly enlarged, and followed up till the 
rest of the face disappear, — a remark that cannot fail to present 
itself to every observer. I founded upon it the division of the 
whole crystalline forms into simple and compound forms ; 
to the latter of which I gave the name of combinations , 
in a sense somewhat different from that of Hauy, who called 
simple forms des combinaisons une a une , and, always proceed- 
ing from his theory, rather meant by them combinations of laws 
of decrement, than combinations of the forms themselves. 
Some of the combinations, besides rhombohedrons, contain at 
the same time several other forms. By the same modes which 
afforded the series of rhombohedrons, I was very soon led to 
the method of deriving those forms likewise from the rhombohe- 
dron, and of arranging them intq series. Thus, I established the 
idea of an assemblage of several series of forms, homogeneous 
among themselves, each of these series having its particular limits, 
and composed of members, that, by the relations they bear to 
each other , acquire the property of entering into those combina- 
tions which nature produces. These series I have called series 
of crystallizations , in order to distinguish them from the single 
series of homogeneous simple forms of which they consist. 
If we examine the productions of nature, according to the idea 
of the series of crystallization thus developed, we find that some 
of them very nearly agree with each other, inasmuch as their series 
of crystallization consist of similar series of simple forms; while 
others, similar among themselves, differ entirely from the former, 
inasmuch as they do not contain any one of the series which 
constitute these ; but nevertheless consist of other series of sim- 
ple forms, similarly connected among themselves, and likewise 
contained within their regular limits. For this, reason, I found it 
necessary to render more striking the connections which exist a- 
mong the former, and the differences between those and the 
latter, which again required a further subdivision ; and this I 
have effected, by giving the name of a System of Crystallization 
to every assemblage of homogeneous series of crystallizations. 
The four systems established in this manner I have called, as 
