830 On the Composition of Water from the Coal-strata. 
On the doubly-refractive character of Thermophyllite, 
Some crystals of thermophyllite, a mineral of which an analysis 
by Mr. Northcote was published in the Philosophical Magazine 
for October 1858, were too imperfect to be measured, or to 
exhibit coloured rings when examined with a polarizing instru- 
ment haying three lenses of equal focal length, resembling the 
instrument contrived by the Astronomer Royal (Cambridge 
Philosophical Transactions, vol. iv. p. 199). Nérrenberg’s 
newest polarizing instrument, in which the focal length of the 
eyepiece is many times that of the other two lenses, or com~- 
binations of lenses (Grailich, Arystallographisch-optische Unter- 
suchungen, p. 43), though it does not allow the positions of the 
optic axes to be determined with much accuracy, permits the 
use of a proportionably smaller slice of crystal. With an instru- 
ment constructed on this principle it was not difficult to make 
out the existence of two optic axes in thermophyllite, making 
with each other an angle of about 22° 30! in air. The position 
of the bisectrix with respect to the cleavage could not be measured 
on account of the curvature of the latter. It appeared to be 
perpendicular to the cleavage. It is therefore probable that the 
crystals belong to the prismatic system, 
XLIV. On the Composition of Water obtained from the Coal- 
strata, Bradford Moor, Yorkshire. By ¥. A. Ane., Hsq.* 
ss ina analysis of a sample of water from the above source 
was undertaken a short time since with the view to ascer- 
tain whether it was adapted to general domestic purposes. The 
results furnished by the examination appeared of sufficient in- 
terest to warrant their publication. 
Two samples of the water collected at the mouth of a coal-pit, 
at an interval of about one month (the separate analyses of which 
furnished thoroughly concordant results), were submitted to me 
officially for examination by Lieutenant Colonel Hamley, Com- 
manding Royal Engineer at York, who informed me that the 
water, which is highly esteemed in the neighbourhood for drink- 
ing and culinary purposes, is raised from coal-pits, at a depth 
of about 200 feet beneath Bradford Moor,—an abundant and 
regular supply being obtained. 
The specific gravity of the water was 1000°78 at 60° F. Its 
reaction was powerfully alkaline, and its flavour was brisk and 
agreeable. 
The proportion of solid matter obtained on evaporation 
* Communicated by the Author. 
