. 84. 85. OF THE CONNEXION OF FORMS. 69 



of a Moveable Plane, tangent to the uppermost 

 point of a vertical rhombohedral axis in a form of 

 several axes. 



The last process refers only to those forms which possess 

 several axes ; while the three methods of derivation de- 

 scribed above, are more particularly intended for such as 

 have only one axis. The fourth process produces only 

 simple forms. 



. 84. POSITION OF THE DERIVED FORMS. 



By the application of these processes of deriva- 

 tion, the derived forms are obtained in such posi- 

 tions in respect to the given one, as will enable 

 them to produce symmetrical combinations, both 

 with the given form, and among each other. 



In forms of several axes, this is the parallel position 

 (. 43.). In those of only one axis, it must be determined 

 in particular, according to the quality of the forms con- 

 cerned. It is sufficiently demonstrated by all compound 

 forms occurring in the individuals of the mineral kingdom, 

 that the simple forms of which they consist, in every in- 

 stance are found in such positions as are assigned to them 

 by the derivation and by the connexion which it produces 

 between forms of a certain quality. 



. 85. SERIES. 



If one of the processes described above yields 

 a derived form of the same kind as the given form, 

 the same process may be applied also to this 

 derived form ; and not only to this, but also to the 

 new product of the derivation, and so on. The as- 

 semblage of forms thus produced, and following 

 each other, is termed a Series. 



