TABLE OF SECONDARY FORMS. 



IT may be observed in the preceding tables of 

 modifications, that many of the secondary forms of 

 crystals, are similar to some of the classes of the pri- 

 mary. And it may also be remarked, in many in- 

 stances, that the secondary forms when complete, or 

 the new figures, as they are termed, are different from 

 all the primary forms. 



The following table exhibits the relations of both 

 these descriptions of secondary forms to the several 

 classes of the primary from which they might be pro- 

 duced; and it may thus be regarded as a kind of 

 index to the tables of modifications. 



The first column contains a list of the secondary 

 forms, several of which are exhibited in their com- 

 plete state, or as they would appear if they were 

 contained within the modifying planes only. 



The second column contains the references to the 

 classes of primary forms, and of modifications, from 

 which the figures in the first column might respec- 

 tively result. 



A single example will sufficiently illustrate the use 

 of this table. 



If we desire to know from what primary form a 

 right square prism may be derived, we find that it 

 may result from its own modification d; or from an 

 octahedron with a square base, by the concurrence, 

 on one crystal of that form, of the modifications a and 

 e, or a and w, when those modifications efface the pri- 

 mary planes. And if we turn to those modifications 

 of the octahedron with a square base, we shall observe 

 that modification a would produce the terminal 



