$82 Professor Molls’ Reply to Professor Weiss, 
of the Natural History Method in mineralogy ; and during my 
stay at Edinburgh, in the spring of 1818, this manuscript, together 
with the drawings belonging to it, and a collection of models I 
had got made in Gartz, for the purpose of illustrating the series 
of crystallization, was two months in your hands : you yourself 
translated some passages from it, and inserted them, according 
to mutual agreement, into the third edition of your valuable 
System of Mineralogy. 
You are not, however, the only person in Edinburgh who 
at that time became acquainted with my method, and what be- 
longs to it ; for I had the honour of explaining the series and 
the systems of crystallization, with the assistance of my models, 
to Mr Thomas Allan, Captain Brown, and the late Professor 
Playfair, in the presence of Count Breunner, whom I accom- 
panied on this journey *. Dr Von Schreibers, the Director of 
the Imperial Collections of Natural History at Vienna, has like- 
wise, at a very early date, v been acquainted with all these sub- 
jects ; and at least a year previous to the composition of the 
manuscript, I communicated to him a paper containing a suc- 
cinct view of my method, the exact contents of which, however, 
I cannot now indicate with certainty. 
On my road to England I also touched at Berlin, where I 
more than once had the pleasure of conversing with Professor 
Weiss. If at that time he had mentioned his paper, or if it 
had been printed, and had communicated it to me, it would have 
put it in my power to lay before him my manuscript. Even 
if, after my arrival at Freyberg, he had sent it to me, I might 
have answered with that part of the manuscript still in my pos- 
session, which refers to Crystallography ; and, I dare say* Pro- 
fessor Weiss would have convinced himself, in the most direct 
way, that, when I came to Freyberg, I in reality knew more 
of the matter than he explained in his Memoir De Indagando, &c. 
The manuscript contains almost every thing you will find iri 
the first volume of my Treatise on Mineralogy, excepting the in- 
troduction, for which I have substituted a shorter one. As to the 
crystallographic part, it contains, 1st, A general consideration 
of the forms, enlarged afterwards only by a few definitions. 9.dly, 
M. Mohs also explained his System of Crystallography to Dr Brewster.— -E d. 
