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Art. XVIII . — On the Methodical and Natural Distributim 
of the different Systems of Crystallisation. In a letter from 
M. Weiss, Professor of Mineralogy in the University of 
Berlin, to Dr Brewster. 
Sir, 
I have learned from Professor Tralles, that he had conver- 
sed with you on the subject of my claims to the methodical and 
natural distribution of the different systems of crystallization, 
which has recently been considered in Scotland *, mid even in 
Germany, if we judge from the Annales de Physique of M. 
Gilbert, as belonging to M. Mohs, but which, in reality, is ab- 
solutely mine. Mr Tralles likewise informed me, that you 
were disposed to repair any injury to my claims, which may 
have been occasioned by the silence of M. Mohs, in the justly 
celebrated work, of which he has published two editions in the 
years 1820 and 1821 ; and I have, therefore, addressed to you 
some observations, which I trust you will publish in your va- 
luable Philosophical Journal. 
In order to enable you to judge in this matter, it will be suf- 
ficient to examine the Table of Mineral Species, distributed ac- 
cording to the method in question, which accompanies a Memoir 
printed among those of the Physical Class of the Royal Acade- 
* When I wrote the two papers, “ On the Connection between the Primitive 
Forms of Crystals, and the number of their Axes of Double Refraction,” which 
were printed in the Memoirs of the Wernerian Society, vol. iii. p. 50. and 357., I 
was not acquainted with any of the memoirs on crystallography, which had been 
composed by Professor Weiss ; and was, therefore, led to quote only the u Charac- 
teristic” of Professor Mohs, which was then publishing in Edinburgh, and which 
contained a classification of crystalline systems, that harmonised in so extraordi- 
nary and unexpected a manner with the optical system which I had previously es- 
tablished. With regard to the extent to which Professor Mohs has been anticipa- 
ted by Professor Weiss, we cannot at present decide, till we have perused the me- 
moirs of the latter referred to in the following pages ; but from what we know of 
the honour and high character of Professor Mohs, we are convinced that he will be 
able to give Professor Weiss the most satisfactory explanations on all the points to 
which he refers. That both these eminent individuals have been carrying on inde- 
pendent inquiries, and advancing greatly the science of crystallography, cannot be 
questioned ; and w r e do not doubt but that this field of research is sufficiently rich 
and extensive, to reward the genius and industry of both. D. B. 
