318 PUMPING OPERATIONS. CHAP. XV. 



emptying out an almost incredible quantity of water. 

 It was found that the water, with which the bed of sand 

 extending over many miles was charged, was to a certain 

 degree held back by the particles of the sand itself, and 

 that it could only percolate through at a certain average 

 rate. It appeared in its flow to take a slanting direction 

 to the suction of the pumps, the angle of inclination 

 depending upon the coarseness or fineness of the sand, 

 and regulating the time of the flow. Hence the distri- 

 bution of the pumping power at short intervals along 

 the line of the tunnel had a much greater effect than the 

 concentration of that power at any one spot. It soon 

 appeared that the water had found its master. Pro- 

 tected by the pumps, which cleared a space for engineer- 

 ing operations in the midst, as it were, of two almost 

 perpendicular walls of water and sand on either side 

 the workmen proceeded with the building of the tunnel at 

 numerous points. Every exertion was used to wall in the 

 dangerous parts as quickly as possible ; the excavators and 

 bricklayers labouring night and day until the work was 

 finished. Even while under the protection of the im- 

 mense pumping power above described, it often happened 

 that the bricks were scarcely covered with cement ready 

 for the setting, ere they were washed quite clean by the 

 streams of water which poured down overhead. The 

 men were accordingly under the necessity of holding 

 over their work large whisks of straw and other ap- 

 pliances to protect the bricks and cement at the moment 

 of setting. 



The quantity of water pumped out of the sand bed 

 during eight months of incessant pumping, averaged 

 two thousand gallons per minute, raised from an average 

 depth of 120 feet. It is difficult to form an adequate 

 idea of the bulk of the water thus raised, but it may be 

 stated that if allowed to flow for three hours only, it 

 would fill a lake one acre square to the depth of one 

 foot, and if allowed to flow for one entire day it would 



