118 Professor How on Gyrolite occurring with Calcite. 
and a general accordance is observed sufficient to show the identity 
of chemical composition in the minerals examined ; the small quan- 
tity of potass present in my specimen probably modified the blow- 
pipe characters a little, as 1 found it not to exfoliate completely, 
and it fused without any difficulty, and even with some boiling. 
Some of the numerous cavities in the apophyllite were empty, 
some entirely filled with gyrolite, and in others separate plates of 
this mineral were standing edgewise, leaving vacant spaces, while, 
upon and by the side of the plates were in some cases rhombohedral 
crystals, which proved to consist of calcite, and were sometimes 
present alone in the cavities, which varied from being quite shallow 
to half-an-inch in depth. It is mentioned by Anderson that gyro- 
lite occurs associated with stilbite, laumonite, and other zeolites, 
and is sometimes found coating crystals of apophyllite. 
The difference in chemical composition between apophyllite 
and gyrolite is very well seen on comparing the respective theo- 
retical percentages of their constituents ; thus, 
SiO. CaO. KO. HO. 
Apophyllite, =52°70 26-00 4°40 16:70-+ HF variable ; 
Gyrolite, =52:18 32-26 15°50; 
and the existence of the calcite in the cavities seems clearly to show, 
that the gyrolite is formed from the apophyllite by the action of the 
water which deposited the carbonate of lime, reacting on the silicate 
of potass, and dissolving out at the same time the fluorine or fluoride 
of calcium ;* trial was made for fluorine on two fragments of the 
gyrolite, and no evidence of its existence obtained. 
REVIEWS AND NOTICES OF BOOKS. 
The Quadrature of the Circle: Correspondence between an 
Eminent Mathematician and James Smith, Esq. 
This is a beautiful book, both inside and out, It is a goodly 
octavo volume, printed in a type which does infinite eredit to the 
Liverpool press; and the binding, too, is mauve,—such a pretty 
colour! On opening the volume, and beginning at the beginning, 
we found page 1 occupied with conveying the information that 
“The right of translation is reserved.’ This circumstance in- 
duced us to believe that the work was intended to be a serious 
essay. But, on reading a few pages of the introduction, some- 
* Dana’s Mineralogy, i. p. 332, 333. 
