of the different Systems cf Crystallisation. 105 
Mohs was at a distance from his place of residence. You will, 
no doubt, observe, that, with regard to the foundation of the ma- 
thematical properties, what M. Mohs has said of Feldspar is ex- 
actly conformable to the views which I had established in 1816 ; 
but M. Mohs is silent on this point, and his method of repre- 
senting the object is in reality his own, and not mine. With re- 
spect to Epidote, M. Mohs remarks, in the second edition of his 
work, when he ought to have been in possession of my memoir 
on epidote, that this very system was unknown. 
It has fallen to my lot, however, to break silence on these mat- 
ters. You will find in the volume of the Memoirs of the Aca- 
demy of Berlin for 1820 and 1821, which will presently appear, 
a new memoir on Sulphate of Lime, and it is there, where, in 
criticising what M. Mohs has said on this subject, that I have 
made the reclamation which it was necessary for me to do ; and I 
should have confined it to that memoir, had not the friendship 
of Professor Tralles led him to give you more immediate and 
direct information, and engaged me to address this letter to you, 
— an engagement for which I feel under great obligations to him. 
It will readily occur to you, that as I had read to the Royal 
Academy of Berlin, the memoirs of which I have now spoken, 
after the year 1815, when I had the honour of being elected 
a member, it must have been a long time before this that I laid 
the essential foundation of the system. In the winter of 1812,18, 
I communicated to my illustrious colleague, M. Von Buch, the 
outline of the same table which is added to my memoir of 1815. 
I employed it in my lectures shortly after that time ; and, in 
teaching mineralogy at Berlin, after 1810, I introduced what I 
had previously done on these subjects. 
You are aware that, in 1809, I wrote at Leipsic, where I 
was then Professor, two Latin dissertations, 64 De Indagando 
Form arum Crysiallinarum Character e geometrico principalis 
which were translated into French, by my esteemed and cele- 
brated friend M. Brochant de Villiers, and appeared in detail in 
the Journal des Mines for 1811 *. Whoever was a profess- 
ed mineralogist, ought to have been acquainted with the exis- 
tence of these memoirs, the French translation of which was 
* Tom xxix. Cah. Mai et ./urn, p. 382.,— 387., & 440. 
