364 Dr Brewster’s Reply to Mr Brooke's Observations 
any foundation at all as a general principle ; he is not told of' 
its successive triumphs over every positive objection that has 
been urged against it ; but he is hurried at once, and without 
ceremony, to witness its demolition. 
Unwilling to occupy my time with such discussions, and be- 
lieving that Mr Brooke’s observations would pass unnoticed by 
the great body of his readers, I had resolved to content myself 
with a private reply ; but I observe, in the last Number of the 
Annals of Philosophy , that its learned editor has quoted the 
whole of Mr Brooke’s animadversions as something important 
to science , and has thus given additional currency to the only 
part of his book which is not characterised by that sagacity and 
discrimination which mark all the writings and labours of its re- 
spectable author. I feel myself, therefore, called upon to ana- 
lyse the objections of Mr Brooke ; and, in order that I may 
not misrepresent his reasoning, I shall print every syllable that 
he has written upon the subject under discussion. 
“ Dr Brewster (says he) has, with that attachment which we usually 
evince towards a favourite pursuit, given a preference to the optical 
characters of minerals, as the surest means of determining their spe- 
cies. See a memoir by Dr Brewster in the Edin. Phil. Journ. vol. vii, 
p* 12. 
“ This memoir relates to a difference in the optical characters of 
the apophyllites from different localities, upon which Dr Brewster 
proposes to erect a particular variety into a new species, under the 
name of Tesselite. Berzelius, as it appears from a paper preceding 
that of Dr Brewster, in the same volume of the Journal, has, at Dr 
Brewster’s desire, analysed the Tesselite, and found it agreeing per- 
fectly, in its chemical composition, with the apophyllites from other 
places. Chemically , therefore , the Tesselite does not appear a distinct 
species.” 
The conclusion, as now stated by Mr Brooke, I must positive- 
ly deny. It will be seen from a note, presently to be quoted 
from Mr Brooke’s work, that lie is not acquainted with the op- 
tical structure of Tesselite, and that if he has seen it, he has 
neither studied nor understood it. Tesselite is a crystal posses- 
sing the most extraordinary structure, — a structure which de- 
fies all the laws of crystallography. It is a substance beauti- 
fully organised by material laws, of which we cannot even form 
a conjecture. It is a substance built up, as it were, of the most 
singular elementary parts, all of which parts have different op- 
tical and mechanical properties. Hence an analysis of Tesse- 
