280 Professor Molls ‘'Reply to Professor Weiss, 
whatever that contains a prism, which, by itself, is a form of 
infinite dimensions. For he indicates finite dimensions of such 
forms, and these he must derive from the dimensions of a se- 
condary simple form of the species, by which proceeding, in 
fact, that secondary one becomes the real fundamental form. 
Thus, if we do not attend to the mere geometrical distribution 
of Haiiy’s primitive forms (which indeed has never been preju- 
dicial to his determinations), we find in his works not only those 
approximations which Professor Weiss mentions in his memoir, 
but also several others, at least as interesting as these, and 
which might very well lead to what M. Weiss calls Systems of 
Crystallization, provided we have previously conceived a correct 
idea of these assemblages . 
In the same memoir, M. Weiss confounds, or at least does 
not sufficiently distinguish between the dirhombohedrons and 
the isosceles six-sided pyramids ; an inaccuracy introduced by 
Hauy, and not removed by M. Weiss, since it is still to be 
found in his most recent papers. Yet the accurate distinction 
of these forms is of the greatest importance. It is, however, 
impossible to get at it, without possessing correct ideas respect- 
ing the simple forms and their combinations, the position which 
the former affect, and the series which they constitute. 
I shall not deny that a person who is already acquainted 
with these assemblages, may trace the first rudiments of Pro- 
fessor Weiss’s System of Crystallization in the memoir in ques- 
tion ; yet, on the other hand, we cannot but confess that it is 
impossible to be led to them by these papers. On this account 
at least, I do not see any reason why I should regret the loss 
I may have incurred by my late acquaintance with them.' 
The paper of Professor Weiss, to which we must here 
attend more particularly, is his General Exhibition of the Dif- 
ferent Natural Divisions of the Systems of Crystallisation, 
read 14th December 1815. The Memoir's of the Society of 
Berlin of the year 1814 came out in 1818 ; the above paper of 
Professor Weiss, therefore, was not printed, or at least not pub- 
lished, till that time. Professor Weiss has had the kindness to 
present me with several of his later papers, exactly as he re- 
marks in his letter; that one was not among the number, be- 
cause, he says, I was at that time at a distance from my place 
