SPRINGS. 317 
The waters obtained from the Middle Lias are especially liable 
to variation in quality as well as quantity, as the rock-beds which 
constitute the chief water-bearing strata possess very different 
characters in different places, passing from an earthy iron- shot 
limestone to a rich ironstone. These waters in many places are 
more or less chalybeate. 
The average temporary hardness of the Lias waters is stated 
to be about 20 ; but in the " Report on the Domestic Water 
Supply of Great Britain," waters obtained from strata overlying 
the Upper Lias clay are included with the Lias waters.* 
Waters obtained by shallow wells in the Lias limestones are 
liable to contamination from artificial sources. 
With regard to the water-supply as affecting health, it has been 
ascertained by Mr. E. E. Berry that goitre occurs in villages 
(supplied with more or less ferruginous water), on the Middle 
Lias tracts from the neighbourhood of Banbury through 
Gloucestershire and Somersetshire to near Sherborne in Dorset- 
shire. 
Reservoirs. 
Reservoirs to supply water for household purposes and to feed canals, have 
been constructed, on the Lower Lias near Chard, at Barrow Gurney, at the foot 
of Robin's Wood Hill near Gloucester, at Witcomb, at Child's Wickham, 
Hewlets near Cheltenham, Chattercutt near Cropredy, Bodington, Wormleigh- 
ton, Napton, north of Daventry (two), near Welford, and Denton ; on the 
Middle Lias at Chilcombe Bottom, Swainswick (partly Upper Lias p), Dowdes- 
well near Cheltenham (Lower and Middle Lias), W. of Naseby, and Knipton ; 
and on the Upper Lias at Monk's Wood, S. of Cold Ashton (partly Middle 
Lias ?), and at Ravensthorpe. Small ornamental lakes have been made in many 
parks on each division of the Lias. 
Springs. 
While the general flow of the rain that falls on the Liassic and 
Oolitic hills is towards the south-east, along the dip-slope of the 
strata, yet notwithstanding this inclination, many springs issue 
along the escarpments at the base of the porous rocks. 
Such springs originally issued when the strata became sur- 
charged with water, and the outflow of water over the clays would 
tend to form in them channels, which in course of time would be 
deepened. Eventually the more important of these springs, 
draining large areas, would become of a permanent character, so 
that a system of underground water-courses exists. 
The porous strata being natural reservoirs for the rainfall, 
overflow springs are found to issue not merely from the base of 
the strata, but where the beds are at all tilted, and succeeded by 
impermeable strata, springs may issue from the upper part of the 
porous beds, and flow along in the direction of the dip-slope, over 
the succeeding clayey formation. 
Streams flowing across the outcrop of porous beds are known 
in places to lose much in bulk from percolation ; but such instances 
* Sixth Report of Rivers Pollution Commission, 1874, pp. 83, 79, 95, 117, 126. 
