164 CELESTINE DEPOSITS OF THE BRISTOL DISTRICT. 
even at this depth the ends of the veins have not yet been 
reached. There are at present about five deposits visible. 
Some of the associated Coal Measure clays are full of small 
detached crystals of celestine. 
The origin of celestine is a question which to me has never 
been satisfactorily explained. It seems that it was either 
deposited from the waters of the Triassic lakes or from mineral 
springs which must have been fairly active during this period 
in this locahty. 
The finding of celestine deposited on hazel nuts and other 
things in the Bath mineral waters would support the mineral 
spring theory, but it might be that the water containing 
carbonic acid passed through a bed of celestine which dissolved 
the strontia which was again re-deposited. 
With one exception I have never seen anything approaching 
a pipe which one would expect to find if the deposit originated 
from a mineral spring. In the cutting of the South Wales 
Rehef Railway at Wapley, sections of small beds of celestine 
were exposed, but there was no sign of a pipe, it being rather 
as if the celestine had been deposited in pools. The exception 
referred to is that at Yate, where the beds run downwards, 
and the bottom has not yet been reached. 
Process of Manufacture. 
Two methods are employed for the preparation of strontium 
salts. In the first the sulphate is fused with sodium carbonate, 
and the resulting mass treated with water. Strontium carbo- 
nate which is formed is insoluble, whereas the sodium sulphate 
is soluble ; the former is consequently easily washed and 
obtained in a state of purity. 
The second method which is considered the better of the 
two, consists in calcining a mixture of powdered celestine and 
coal. A sulphide of strontium is formed which is dissolved in 
water and converted into the carbonate by blowing carbon 
