ON THE CIRCULATION OF UNDERGROUND WATERS. 123 



The high permeability of the New Red Sandstone is remarkably shown in 

 the Green-Lane well of the Liverpool Corporation waterworks, of which the 

 details were furnished to Prof. Hull by Mr. Duncan, the resident engineer. 



The well was sunk in 1845-46, at a point 144 feet above the sea-level, to a 

 depth of 185 feet, or 41 feet below the sea. The yield was then 1,500,000 

 gallons per day. 



A 6-inch bore, sunk 60 feet from the bottom of the weU, increased the 

 yield to 2,317,000 gallons. 



In June 1853, the supply having slightly fallen off, the bore-hole was 

 deepened a further 381 feet, when the yield increased to 2,689,000 gallons. 



In June 1856 the bore-hole was widened, and carried a further 101 feet, 

 when the supply rose to 3,321,000 gallons per day. 



In the first boring, as pointed out by Prof. Hull, the increase was at the 

 rate of 17,783 gallons per foot, in the second it was only 9789 gallons per 

 foot, and the third only yielded 6277 additional gallons per foot ; so that 

 increase of depth gives so rapidly a diminishing ratio of volume, that a zero- 

 point woiild be soon attained. 



The large volume of water in this well is believed to be due to the existence 

 of a large fault, which acts as a duct for the underground waters over a large 

 area. 



The water from the Green-Lane well was anah'zed in 1850 by Mr. Philhps, 

 and one gallon contained : — 



grains. 



Carbonate of lime 5-26 



Chloride of sodium 2-66 



Sulphate of soda 2-23 



Silica 0-64 



Organic matter, &c 2-81 



13-60 



Mr. Isaac Eoberts, who has given much attention to the wells of Liverpool, 

 found by experiment that one square foot of compact sandstone 10| inches 

 in thickness, of average coarseness, allowed the following quantities of water 

 to pass through it per hour : — 



At a pressure of 10 lbs. to the square inch 4^ gallons. 



J> » "0 „ „ 1% 5> 



» j> 46 ,, » ly „ 



the increase being nearly directly as the pressure. 



Mr. Eoberts examined the Liverpool sandstone microscopically, and found 

 it to consist of roughly rounded grains of quartz attached at the points of 

 contact with a siliceous cement. When a block of this sandstone is immersed 

 in water, the grains do not absorb but attract the water into the spaces 

 between the grains by capillary attraction — sandstone of ordinaiy coarseness 

 taking up no less than J^ of its own weight of water, of which J^ runs away 

 by the influence of gravity, the remainder being held in the cavities of the 

 stone by capillary attraction. 



Mr. Roberts describes seven wells which he has sunk or deepened at 

 Liverpool, and gives information concerning them, which clearly proves the 

 gradually lessening amount of rainfall which can make its way into the 

 ground through the large extent of area in Liverpool covered with buUdings 



