vol. xx. (i) MINERAL WATERS NEAR GLOUCESTER 
37 
sodium would be at liberty to unite with sulphuric acid, a 
product formed by the oxidation of the sulphuretted hydrogen, 
a body usually found in the intestines of most vertebrates. In 
this way sodium sulphate would become a waste product and 
would accumulate in the soil. As this may seem a little involved 
I will state the facts on which I have relied. 
First, vertebrate animals use salt ; secondly, salt is decom- 
posed in the digestive processes ; thirdly, sulphuretted hydrogen 
or other sulphur compounds are plentiful in the intestines, and 
my inference is that the oxidised sulphur compounds form 
sodium sulphate with the liberated soda from the common salt. 
If my suggestion be accepted, then the amount of sodium 
sulphate may give some indication of life existing during the 
formation of the rocks. 
As to the calcium sulphate (Gypsum), this presents no 
difficulty, as w r e can watch its formation at the present time. 
On the black shales at the Garden Cliff, Westbury, may be 
seen numerous star-shaped masses of white crystals consisting 
of Gypsum, and their mode of formation may be easily observed. 
Many of the beds contain abundance of Iron pyrites (Sulphide 
of Iron), and these on exposure to air and w r ater oxidise, forming 
Oxide of Iron and Sulphuric Acid. This acid, passing through 
limestone, decomposes the carbonate of lime, forming with it 
the calcium sulphate. The solution then dries on the shale, 
and the crystal masses to which I have referred above are 
formed. 
The origin of the Iron is quite understandable. It is partly 
derived from the bodies of animals during decomposition, and 
also by the gases given off uniting with the iron in the rocks. 
The strongest Chalybeate waters in this district are derived 
from the Marlstone and from the recent deposits covering the 
Low r er Lias. 
The traces of Iodides and Bromides have the same origin 
as the Sodium Chloride wffiich they accompany. 
. Whence come the Lithium and Thallium ? I know not. 
As to the radioactive matter, it is too little known to permit 
of even a wild guess. 
The only gas of importance for which I have to account is 
