EL GOLEA. 415 



the style of Wargla, it has made its mark in history, 

 and was considered impregnable by the Arabs. El 

 Golea is 101 French leagues, or ten days' caravan 

 march from Insalah, * mostly passing through the 

 sands of the " Sahara-el-Falat " or Waterless desert. 



But reverting to the important question of Artesian 

 wells, however, the geological features of the Sahara 

 region, and the low level at which the basin of that 

 great desert lies, render it by no means improbable 

 that the enterprise of a Trans-Saharian railway may 

 be successfully accomplished by their means either 

 wholly or in part; and where the Artesian principle 

 failed, there would still remain the time-honoured plan 

 of the ordinary shaft, from which the water can be 

 raised by pumps ; and though the question is somewhat 

 foreign to the general scope of these pages, it may 

 perhaps be well to mention that the principle of the 

 Artesian well consisted* of boring down through beds 

 of clay, chalk, or other strata, impervious to water, 

 until a porous bed of gravel, etc., is reached; and if 

 this water-bearing stratum dips, from the point where 

 the water enters until it reaches the place where the 

 spring is tapped, the water will naturally rise in the 

 well, and in some cases where the pressure is considerable, 

 as for instance where it proceeds from a greatly higher 

 level, the water may gush out at the top in a plentiful 

 stream. A good example of this latter result is furnished 

 by the well-known Artesian well at Grenelle, near 

 Paris, sunk by M. Mulct, to a depth of 1802 feet. 

 It was brought to a successful termination in Feb. 

 1841, after eight years' work, at a cost of about 



* Le Sahara Algerien, par M. le Lieut.-Col. Daumas, Paris 1845, 

 p. 320. 



