I860.] Hull on Water supply from New Red Sandstone. 



423 



siderable areas around. The porous character of the rock also finds 

 auother ciu'ious illustration in the case of some of the Liverpool wells. 

 Out t of four large wells in the 

 lower part of the town, three 

 have become charged with briue 

 from the sea, owing to the extrac- 

 tion of the fresh water, and the 

 general lowering of the water- 

 level in the rock. The most re- 

 markable case is that of Mr. 

 M'Gregor's "Well, situated at a 

 distance of 1,200 yards from the 

 shore, which now yields salt 

 water. The cause of this is 

 not difficult of discovery. Be- 

 fore pumping operations were 

 commenced at Liverpool, the 

 water-level in the rock was the 

 same as that of the sea close to 

 the shore, but inland gradually 

 rose with the surface of the 

 ground. Thus, when the Green 

 Lane Well was first sunk, the 

 water-level was found to be only 

 38 feet from the surface, or 106 

 feet above the sea. The sinking 

 of many wells, and the extrac- 

 tion of the water from the rock, 

 necessarily tend to lower the 

 water-level, and near the sea to 

 bring it below the sea-level. 

 The balance of the water in the 

 rock, and that of the sea being 

 thus destroyed, the sea-water 

 forces a passage for itself in- 

 wards. The water-level at Green 

 Lane is now 70 feet from the sur- 

 face, that is, 32 feet lower than 

 when the well was first sunk. 



Notwithstanding the porous 

 character of the rock, the process 

 of percolation is extremely slow, and on this account the sinking of a 

 well has little or no effect on the vegetation, and sometimes a shallow 

 well is not perceptibly affected by the neighbourhood of a deep one. 

 But a more remarkable result still remains. It has been found that 

 the yield is greater in the summer — that is, in the six dry months — 

 than in winter — the six wet ones. Mr. Hawksley, whose experience in 

 these matters is undoubtedly large, stated in evidence before a Par- 

 liamentary Committee during the present Session, that of the total 

 quantity of water drawn from deep wells in certain situations, 2-5ths 

 are supplied during the six winter months, while 3-5ths are supplied 



Fig. 2.— General Section of a Well, with Chambers 

 and Bore-hole. 



