19^ Mr Brooke’s Remarks on Dr Brewster's Reply 
chemically , appear a distinct species of mineral f and he follows 
up his quotation with this remark : 64 The conclusion, as now 
stated by Mr Brooke, I must positively deny .” A reference to 
some facts might surely have been expected from Dr Brewster, 
in support of this denial ; but not a syllable of proof follows. I 
shall, therefore, attempt to supply those evidences which Dr 
Brewster has omitted. 
In considering the chemical character of the apophyllites, it 
will be necessary to recur to the two papers on this subject, com- 
mencing at page 1. of the 7th volume of this Journal. On re- 
ferring to the first of these, it will be seen that Sir George Mac- 
kenzie had sent to Berzelius some specimens of the mineral 
named Tesselite by Dr Brewster ; and that these were, at the 
desire of Dr Brewster, analysed by Berzelius. This gentleman 
also analysed specimens of the Apophyllite from Uto, and found 
their composition similar to that of the Tesselite. In page 18., 
Dr Brewster says, u I have reason to believe , that the Tesselite 
exists among the Apophyllite of Uto ; and therefore it is not im- 
probable that Berzelius may have analysed the Tesselite from 
Uto? Would it not have been more satisfactory to his readers, 
if Dr Brewster had assigned the reason which induced him to 
believe that his Tesselite had been found at Uto? The ten- 
dency of Dr Brewster’s conjecture was to rid himself of a fact 
unpropitious to his theory ; and it therefore became more incum- 
bent on his candour to have fully stated the grounds of his be- 
lief. 
Dr Brewster goes on to say, that 66 the two kinds of apophyl- 
lite which are set in peculiar contrast with one another in the 
optical method, are the Apophyllite surcompose of Fassa, and 
the Tesselite of Faroe; and therefore the analysis of these two 
crystals, when the former is perfectly pure , should be well com- 
pared.” Dr Brewster probably was not aware of the analysis of 
the Tyrol Apophyllite , by Gmelin, or he might have himself 
made the comparison he recommends ; and he would then have 
found the Tyrol mineral (but of what form the crystals are, is 
not stated), agreeing as closely in its composition with the Fa- 
roe variety, as the Uto specimens had done. 
The results of the analysis of the three varieties are as fol- 
lows : 
