)rO REPORT — 1855. 



daily, and has continued, without diminution in quantity, since it was com- 

 pleted in 184-1. The supply to the sand from which it rises is said to be 

 derived 100 miles off; and yet such is the pressure, that it rises in a tube to 

 the height of 120 feet above the surface of the ground at the well. 



It is estimated that the quantity of water derived by means of Artesian 

 wells by public and private parties within the city of London or its imme- 

 diate neighbourhood, amounts to 8,000,000 or 10,000,000 gallons per day. 

 This is obtained almost entirely from the lower tertiary sands and the upper 

 beds of the chalk. Probably a much larger quantity could be procured 

 from the greensands below the chalk. Mr. Prestwich, who has most ably 

 entered into an examination of this question, is of opinion that 30,000,000 

 or 40,000,000 gallons of excellent water might be obtained daily in this 

 manner for the supply of London. 



The quality of the water will depend upon the character of the water- 

 bearing stratum from which it is derived; the chalk will generally yield hard- 

 water, the greensands generally soft. The water from the lower tertiary sands 

 is occasionally chalybeate and unsuitable for domestic use. In nearly all cases, 

 the water, after being first tapped, improves in quality as it continues to flow. 



This source of supply is of course only available under certain geological 

 conditions, and is always limited by the amount of water which the water- 

 bearing stratum can absorb from rain or surface drainage, and by the resistance 

 opposed to its free passage by the closeness of the material through which it 

 has to pass. 



Formerly the water in the Artesian wells which are sunk to the chalk in 

 London, rose to the surface and overflowed ; but the number of wells which 

 have been constructed have in great measure exhausted the supply, and the 

 water has now to be raised by artificial means from considerable depths. 



The question of a supply of water by this means is one of great interest. 

 It has been very carefully investigated by many able and competent men — 

 by Mr. Prestwich, the Rev. Mr. Clutterbuck, Mr. Dickinson, Mr. Stephenson, 

 Mr. Braithwaite, Mr. Homersham and others, to whose publications and to 

 the discussions which have taken place in the Institution of Civil Engineers, 

 useful reference may be made. 



The water derived from wells in the new red sandstone forms a closely 

 analogous system of supply. 



Here the supply generally depends upon the porosity of the rock, the 

 quantity of rain which falls upon its surface, the amount of infiltration, and 

 the angle of friction which is formed by the resistance of the rock to t"he free 

 passage of the water. The new red sandstone covers so large a portion 

 of England that its capability for aff'ording water is a question of correspond- 

 ing interest. In some districts it is found to yield an abundant quantity, in 

 others very little. It is generally hard, but well-aerated and agreeable to the 

 taste. 



The largest supplies from this source have been obtained in Liverpool, and 

 owing to the long contest and repeated investigations as to the best means of 

 affording an increased supply to that town, very ample information has been 

 obtained as to the yield of the wells and the quality of the water. The 

 Report of Mr. Robert Stephenson on this subject in March 1850, is full of 

 valuable statistics. It appears that the supply then afforded by the new red 

 sandstone from seven wells or stations, was 3,900,000 gallons per day, being an 

 average of about 570,000 gallons for each well ; but Mr. Stephenson arrived 

 at the opinion that an isolated well in the new red sandstone at Liverpool 

 mi^ht be assumed as capable of yielding about 1,000,000 gallons of water 



