428 
Some of the numerous cavities in the apophyllite were empty, 
some entirely filled with gyroiite, 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- 
iite occurs associated with stilbite, laumonite, and other zeolites, 
and is sometimes found coating crystals of apophyllite. 
The difference in chemical composition between apophyllite 
and gyroiite is very well seen on comparing the respective theo- 
retical percentages of their constituents ; thus, 
Si*0 3 . CaO. KO. HO. 
Apophyllite, =52*70 26*00 4*40 16*70-f- HF variable ; 
Gyroiite, =52*18 32*26 15*50 ; 
and the existence of the calcite in the cavities seems clearly to show, 
that the gyroiite 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 
gyroiite, and no evidence of its existence obtained. 
4. On Natro-boro-calcite, and another Borate occurring in the 
Gypsum of Nova Scotia. By Henry How, Professor of 
Chemistry and Natural History, King’s College^ Windsor, 
N.S. 
About three years and a half ago, I showed the existence of Natro- 
boro-calcite in the gypsum of Windsor, N.S.']' I was not aware at 
that time that Dr Hayes of Boston, U.S., had announced his convic- 
tion]; that the soda which had been attributed to this mineral was an 
impurity, and had given, as the true expression of the composition of 
the pure mineral, the formula CaO 2 BO g + 6 HO. Had I known 
this, I should have adverted to the probability of his mineral 
(Hayesine, Dana) constituting a distinct species from Natro-boro- 
calcite, whose existence seems to be sufficiently established by the 
repeated finding of not very dissimilar quantities of soda in analyses 
* Dana’s Mineralogy, i. p. 332, 333. 
t Edin. New Philosophical Journal, July 1857. Silliman, Sept. 1857. 
X Silliman, Nov. 1854, p. 95. 
