516 LOWER OOLITIC ROCKS OF ENGLAND. 
quantities of iodide and bromide of sodium occur, and the Spa is known 
as the Woodhall Iodine Spa.* 
It is interesting to find that, not far from the church at "Woodhall, at a 
depth of 33 feet, " a spring of salt water waa tapped, resembling that of 
Woodhall Spa, but it gradually became less salt, and was finally replaced 
by a supply of fresh water."f 
In connection with this subject, it is useful to bear in mind that at 
Northampton, saline waters were encountered beneath the Lias, at a 
depth of 650 feet. At Gayton at a depth of 994 feet, below the Lias, 
saline waters were found, and they yielded 1,500 grains per gallon ; at 
Kettering saline water, amounting to 200,000 gallons a day, with 1 ,200 
grains per gallon, was encountered between the Lias and Lower Carboni- 
ferous JJocks.J At Rugby saline-waters were met with in the New Bed 
rocks. 
The occurrence of saline waters is to some extent connected 
with the underground damming up of waters, whereby the saline 
matters, derived in great part from the rocks themselves, become 
concentrated. Hence pumping may in certain cases reduce the 
amount of the ingredients. The occasional outbreak at the surface 
of such springs may sometimes be connected with lines of fault, 
especially in clayey tracts, although it may be difficult to prove 
the existence of these disturbances. 
In others cases the supply of saline matter may be distant and 
become diffused among the Oolitic rocks from deep-seated 
Palasozoic strata, where the newer rocks abut against them : the 
saline ingredients being derived in a measure from the percolation 
of sea-water, or to the descent of water to considerable depths 
among folded Palaeozoic strata where increased temperature would 
lead to increased solution of materials. Synclinal troughs among 
the older strata may receive a considerable amount of saline water 
from the sea, and it may rise as artesian springs among the over- 
lying strata. The saline waters may also be distributed locally 
by means of faults arid fissure?. To some such cause, the saline 
waters of Swindon and the Bath thermal waters may be attributed. 
* A. Strahau, in Geology of Lincoln, p. 208 ; see also A. B. Granville, Spas of 
England, vol. ii. Midland Spas, p. 104. 
f A. Strahan, in Geol. Lincoln, p. 205. 
j De Ranee, 16th Report on Underground Waters, Rep. Brit. Assoc. for 1800, 
p. 374 ; H. J. Eunson, Quart. Journ. Geol. Soc., vol. xl. p. 482. 
