of the different Systems of Crystallisation. 107 
any other distinction, what I had called, in 1809, the system 
having its primitive form an octohedron with an elongated 
rectangular base ; that still later he recognised as natural and 
good, one of the subdivisions which 1 had made in 1815 (or 
rather before 1815), of the same system founded on the gene- 
ral difference of the homoedral and hemiedral systems, he having 
given the name of Hemiprismatic to the one, leaving the name of 
Prismatic to the others; and, in short, that it was not till 1819-&0, 
precisely when the first edition of his Characteristic was pub- 
lished, that M. Mohs recognised another of my subdivisions of 
the same system, and improperly gave to it the name of Te- 
tarto-prisma tic. 
It would be very agreeable to me to receive an explanation 
of the silence of M. Mohs ; for I esteem him much, and he is 
a philosopher who does honour to Germany ; but my silence 
ought not to equal his. For any farther remarks, however, on 
this subject, I shall refer you to my Memoir on Sulphate of 
Lime, which I have already had the honour of quoting. 
The system which is commonly called Regular or Tessidar , 
I have called also Sphreroedrdl , on account of its relations with 
the sphere, which are peculiar to it. It is founded on three 
axes, perpendicular and equal to each other. I have distin- 
guished, however, the ordinary case, which is homo-spheroedral, 
from the different cases of the system which are hemispheroe- 
" dral , and of w r hich we know that of the pentagonal dodecahe- 
dron, which I call the Pyrito-edral System, and that of the 
regular tetraedron or tetra-edral system (regular) ; these two 
cases having quite different laws of the reduction to one-half of 
the same number of faces to reduce, and of which, I believe 
that I have shewn the origin in the different manner of being 
polarised in the Icitera of the three principal axes, in my memoir 
of 1817, already quoted. 
The systems which are founded on three axes perpendicu- 
lar to each other, two of which are equal and different from the 
third, may be named, in relation to this same principle, Bino- 
singulaxia , or Bino-unixal. I had not made a decided subdi- 
vision of this general case in 1815, since Harmotome almost 
alone appeared to me then to give rise to a subdivision into 
homoedral and hemiedral systems, analogous to the other gene- 
