On Artesian Wells. 



81 



As another illustration, let us suppose that the bed of clay 

 rested nearly horizontally on the lower strata containing water, 

 and it will be seen that the same result would follow. The 

 moment that vent was given by the bore to the water, it would 

 be forced by the superincumbent weight to rise in the tube. 

 The superincumbent strata will, as the water flows up, sink 

 down, and continue to force up the water, so long as any re- 

 mains at the bottom of the bore. Indeed, the same reasoning 

 applies to the continuance of the supply of water, even if we 

 admit it as coming from a higher level. To support the latter 

 theory, however, we have seen that it is necessary to admit the 

 dubious fact, of the required water coming from heights some- 

 times at almost inconceivable distances; whereas, by the former, 

 this difficulty is entirely got over. 



The more distinctly to illustrate this, let us suppose a cask 

 or wooden box filled with water, until it reaches the cover 

 A B, which is tightly fitted as a top. Then insert a hollow 

 tube D through the cover A B. When the pressure of the 



cover is increased by the addition of the weights e e, the water 

 will rise to the top of the tube D, and it will continue to over- 

 flow as long as the pressure is made, or the supply continues, 

 The same principles apply exactly to the rise of water, by su- 

 perincumbent pressure, from the bed of clay. If it be argued 

 against this theory, that the supply of water would in time 

 cease, it may be answered, that the same argument obtains, 

 and with equal force, against the other ; for whether the water 

 comes from a higher level, or only from a free level, it should bo 

 remembered, that it has been admitted by the best authorities 

 that artesian wells are sensibly affxjcted by long-continued 

 droughts. 



VOL. XXXV. NO. LXIX. JULY 1843. F 



