LIAS OF ENGLAND AND WALES : 
At the Montpellier Wells saline-chalyl>eate waters were found 
of somewhat different character in different sinkings. No less than 
70 wells were sunk ; in most of them chloride of sodium was found 
to preponderate, but in one case sulphate of magnesia was more 
abundant. Here the surface-strata comprised about 12 feet of soil 
and sand, and sinkings were carried to a further depth of 63 feet 
in the blue clay of the Lias. The water obtained at the greatest 
depth was more highly chalybeate, and contained a larger propor- 
tion of common salt. 
With regard to the Cheltenham waters, it was pointed out in, 
1834 by Murchison, that the most abundant ealine ingredient, sea- 
salt, "is present instill larger quantities in those wells which occur 
near the western edge of the formation, where the Lias form* 
only a thin covering above the marls of the Ne\v .Red Sand- 
stone. At the new spa, near Tewkesbury, where formerly the 
mineral water at shallow depths belo\v the surface was very 
slightly saline, it was recently found to be much more im- 
pregnated with salt when the sinking was carried to the depth 
of 90 feet. * Again, at Cheltenham, when experi- 
mental borings were made by Mr. Thompson, to the depth of 
260 feet below the surface, the water of the lowest stratum of 
marl or clay was found to be more highly charged with the 
chloride of sodium, or common salt, und to contain less of the 
sulphates, than the existing wells, none of which have been sunk 
to a greater depth than 130 feet." 
He explains that " waters collected in the New Red Sandstone 
at higher levels than the surface of the Vale of Gloucester, would 
naturally ascend to their original level by any cracks or open 
veins which might present themselves in the overlying Lias. 
This salt water having to pass through various strata of marl 
and clay, loaded with iron pyrites, or sulphuret of iron, it is 
presumed that during this passage certain chemical changes take 
place, which give to the waters their most, valuable medicinal 
properties." * " In ^suggesting this explanation, we 
must not, however, overlook the fact, that fresh water is per- 
petually falling from the atmosphere upon the surface of the Lias 
clay, more or less percolating its uppermost strata."* 
The view suggested by Murchison, that the saline waters of 
Cheltenham rise from the New Red Sandstone series, is supported 
by Daubeny, who remarks "that during the passage of the 
water upwards through cracks and fissures in the Lias clays 
overlying, the iron pyrites, which is so abundant in that stratum, 
supplies it by its gradual decomposition with the sulphuric acid 
found amongst its ingredients. That sulphuretted hydrogen is 
generated in the vicinity of these springs, we are assured, not 
* Murchison, Geol. Cheltenham, 1834, pp. 33-35 ; Proc. Geol. Soo., vol. i. p. 390 ; 
and Silurian System, pp. 34-36. 
