316 ARTESIAN WELLS. SPRINGS IN DESERTS AND PARCHiHD PLAINS. 



istence of water beneath the surface where the soils rest on impermea 

 ble beds, and the known tendency of these waters to rise when a boring 

 is sunk to them, that have given rise to the establishment j?f Artesi(m* 

 wells, so frequently executed, and with^o much success, in recent times. 

 There is probably no geological fact that promises hereafter to be of more 

 practical value to mankind, when good government and the arts of peace 

 shall obtain a permanent resting-place in those countries where, without 

 irrigation, the soil remians hopelessly barren. Wherever a living spring 

 bursts out in the sands of Arabia, in the African deserts, or in the parched 

 plains of South America, an island of perennial verdure delights the eye 

 of the weary traveller, and wherever in such countries the labour of man 

 has been expended in digging wells, and in raising water from them for 

 artificial irrigation, the same beauty and fertility always appear. It 

 has recently been found that the oases of Thebes and Garba, in Upper 

 Egypt, where the blown sands now hold a scarcely disputed dominion, 

 are almost riddled with wells sunk by the ancient Egyptians, but for the 

 greater part long since filled up. The re-opening of such wells might 

 restore to these regions their long-lost fertility, as the sinking of new 

 ones by our easier and more economical methods might reclaim many 

 other wide tracts, and convert them to the use of man. In contemplating 

 what man may do, when his angry passions and his prejudices do not 

 interfere with the exercise of his natural dominion over dead matter, it is 

 not unreasonable to hope that, guided by such indications of natural 

 science, human industry may hereafter, by slow degrees, re-establish its 

 power in long-deserted regions of country, spreading abundance over the 

 broad wilderness, staying the Arab's wandering foot, and fixing his 

 household in a permanent and plenteous home. 



6°. It not unfrequently happens that alternate layers of sand and clay 

 overspread the rocks of a country, and act in arresting or in throwing out 

 the surface water in the same manner as the solid strata beneath. Thus 



under the surface A B here represented, alternate layers of sand and clay 

 overspread the inclined beds of rock, and alone affect not only the qual- 

 ity but the state of dryness also of the soil. 



The rain which falls on the upper bed of sand will sink no further 

 than the first bed of clay, and will appear as a spring, or will form a 

 wet band along the side of the hill, at a. That which falls or exists in 

 the second bed of sand will in like manner ome to day at 6, c, and d, e, 



millions of gallons weefely. "Ais number of wella has since been increased, and is still 

 increasing. Tiie borings are generally carried down into the chalk, because the water which 

 ascends from the plastic clay has been found to bring with it much sand, which both ob« 

 structs the pipes and is injurious to the pumps. 



* So called from the district of Jr/ots, in France, in which it was formerly sapposed that 

 such borings had been longest or most extensively practised. 



