38 
PROCEEDINGS COTTESWOLD CLUB 
1918 
Sulphuretted Hydrogen, and the origin of this will vary in 
different localities. 
At Llandrindod Wells I think I am in a position to say 
how it originates. 
On the high ground surrounding the town a vein of Galena 
(Sulphide of Lead) exists, and under the influence of air and 
moisture oxidises, the exposed fragments being covered with 
Lead Oxide. The sulphur combining with the hydrogen of the 
water yields the gas which is dissolved and carried through 
fissures of the rocks into the Wells. 
It maybe asked, Does the water become polluted with the 
Lead ? No, it does not, nor cannot, as a portion of the sulphur 
has been oxidised to sulphuric acid and formed the very in- 
soluble lead sulphate. In the many analyses I have made of 
the waters of this district I have not found a trace of Lead. 
The origin of this gas in the waters of this district interests 
us most, but I fear its presence cannot be accounted for with 
as much certainty as in the case above quoted. I think the 
following explanation may be provisionally accepted. 
As most of our medicinal waters are derived from the Lias, 
a series of beds containing both organic matter and sodium 
sulphate, we may conjecture that the sulphate has been reduced 
by the organic matter and the sulphuretted hydrogen set free, 
or in consequence of the frequency of Iron pyrites a reaction 
similar to that at Llandrindod may account for its presence. 
I will conclude with a little speculation in the region of 
Archaeology, in which a study of some well-water will help to 
explain an interesting monument. No doubt you are all 
acquainted with a rather picturesque well in the Cloister Garth 
at Gloucester. At intervals the late Dean asked me to make 
an analysis of the water, but unfortunately I neglected to do 
this during his lifetime, so am unable to know why he was so 
anxious for this to be done. 
With the kind permission of the Archdeacon of Gloucester 
I have now obtained a sample and made an analysis (Table XI.). 
We see from this that it is a surface well of no great depth, 
and could therefore have been of little value as a supply for the 
monastery, and yet it was dignified by the somewhat ambitious 
