176 



ARTESIAN WELLS. 



flows through a bed of gravel overlying clay, and the 

 porous superstratum is alternately saturated by the 

 water of the Thames as the tide rises, and then 

 drained again to the distance of several hundred feet 

 from the banks when the tide falls, so that the wells 

 in this tract regularly ebb and flow. 



We can now understand why water flows out on 

 the surface, at the base, or on the side of a hill ; the 

 upper strata are porous, while the subjacent are com- 

 posed of clay or other retentive soils. Springs 

 which are not affected by long droughts probably 

 owe the constancy and uniformity of their volume 

 to the great extent of the subterranean reservoirs 

 with which they communicate. 



Artesian Wells. — In Artois, in France, a method 

 has long been practised of obtaining water by bo- 

 ring the earth with a large auger from three to four 

 inches in diameter. Hence such wells are called 

 Artesian. This practice is founded on the fact that 

 there are sheets or veins of fresh water at various 

 depths in the earth. When a rock is met with, it is 

 triturated with an iron rod, which is alternately ele- 

 vated and dropped by machinery ; the materials, thus 

 being reduced to a powder, are readily extracted. 

 In this manner Mr. Disbrow, at Holt's Hotel in the 

 city of New- York, penetrated through 126 feet of 

 stratified sands, blue clay, and river mud, when he 

 came to the gneiss rock which underlies the whole 

 island; he then bored this rock 500 feet, the upper 

 200 with an auger 3 inches in diameter, and the re- 

 mainder with two and a half inch. He also pene- 

 trated the earth at the corner of Bleecker-street and 

 Broadway, with an auger 7 inches in diameter, to the 

 depth of 448 feet, 406 of which is in solid rock. 

 This well furnishes 120,000 gallons of excellent 

 water in 24 hours ; and the water rifees within 20 

 feet of the surface. Where the hole is made into 

 the earth, in order to prevent the sides from falling 

 in, as well as the escape of the water into the adja- 



