336 WATEE-BEAPtlXG STEATA. 



The Keuper Marls come first in order, the name being of 

 German origin. They consist of either soft white or grey 

 sandstones, and red and variegated marls, with gypsum more 

 or less thinly bedded, and in the Bristol district are under- 

 lain by the Dolomitic Conglomerate, a water-tight rock, which 

 is the salvation of the coalpits which it overlies, being called 

 by the miners the water-tight overlie. 



The series immediately under the Keuper is the Bunter, 

 consisting of red and variegated marls and Bunter Sand- 

 stone. This division of the Trias is absent in the Bristol 

 District. 



It is from these sandstones (the Keuper and Bunter) that 

 some of the largest cities in England are supplied, notably 

 Birmingham, Liverpool, AVolverhampton, Nottingham, Lich- 

 field, and South Staffordshire. 



In Liverpool there are seven wells averaging to the bottom 

 of the bore-holes (of 6 inches to 8 inches diameter) from 245 

 to 369 feet below mean sea level, these wells being (most of 

 them) sunk within the city boundary, and the eastern area 

 being a bare drift of boulder clay giving high evaporation, 

 a low percolation of not more than from twenty to thirty 

 per cent, of the rainfall is the result. 



The yield of these wells gave an average daily quantity 

 for ten years, ending 1876, of seven to eight million gallons 

 per day. 



The supply is now augmented by the Vyrnwy Lake just 

 finished, situated on the Lower Silurian Kock (with a drainage 

 area of 34 square miles, or 22,000 acres, over which the rain- 

 fall is estimated at 70 inches per annum), at a cost of two 

 millions sterling, but not yet brought into use owing to the 

 stoppage of the tunnel under the Mersey at Fidler's Ferry, 

 on account of difficulties met with by the contractor in a 

 shifting sand when excavating. 



