AS SOURCES OF WATER-SUPPLY FOR TOWNS. 263 



qualities, and depends also to a large extent on its homo- 

 geneity, which we now proceed to consider. 



2. Homogeneity. — The three members of the Bunter di- 

 vision (see above) are very nearly similar in composition, 

 though somewhat differing in solidity. 



The first and third members consist of soft incoherent 

 sandstone, very porous, and readily absorbing whatever 

 rain falls on its surface. The middle member is generally 

 more compact, but in the central counties often passes into 

 a loose conglomerate of quartz -pebbles, also of an ex- 

 tremely porous nature. Therefore, for the purposes of 

 water-supply, the whole formation, attaining a vertical 

 thickness of several hundred feet, may be considered as 

 equally absorbent throughout, being in effect (with occa- 

 sional exceptions) a natural reservoir, the water from which 

 is capable of being utilized by mechanical skill. At the 

 same time it must be recollected that judgment and know- 

 ledge to determine the most effective mode of applying 

 that skill are as necessary in this case as in laying out a 

 colliery, or any similar undertaking. 



That this formation readily yields to the passage of 

 water, both vertically and horizontally, is proved by general 

 experience. The case of the well sunk at Green Lane, 

 near Liverpool, and belonging to the Corporation, illus- 

 trates this point. This well, by sinking and boring, reaches 

 a depth of 385 feet ; and I am assured by Mr. Duncan, the 

 engineer, that the pumping operations influence wells " se- 

 veral miles distant.^^ In fact, I believe it has laid dry all 

 the wells within a radius of a mile. Mr. J. Cunningham, of 

 Liverpool, who has paid much attention to this subject, 

 informs me that some wells in that town, sunk for a quarter 

 to half a mile from the sea-side, have now become so salt 

 as to be useless for household purposes, proving that the 

 sea can make its way inland to this distance at least. Upon 

 this point the evidence is perfectly conclusive ; for we find 



