232 M. Arago on Artesian Wells 



with the lowei" impermeable stratum ; or it will stop before it 

 so come into contact, in a state of equilibrium ; or, finally, it will 

 be subjected to an oscillatory movement. But none of these 

 suppositions agree with what is known concerning the regularity 

 of the flow of many fountains. In the last of these hypotheses, 

 the flow would be intermitting; in the second^ the stream would 

 entirely stop, after the issue had for a time been gradually di- 

 minishing ; and, in the first, there would, sooner or later, be an 

 entire cessation of the stream, especially in those situations, by 

 far the most numerous, where the water-carrying bed is of very 

 limited thickness. 



It would be an easy matter to produce other objections to 

 these theories; but I conceive it will be wiser to examine the 

 bearing of the only specious difficulty which has been stated 

 against the accuracy of the view, that these fountains assimilate 

 in principle to reversed syphons — to souterazi. 



It is this, that some of these fountains, as, for example, those 

 of Lillers in Artois, throw up their waters in the middle of im- 

 mense plains. The most insignificant hillock is not to be descried 

 in any direction, and where then, it is demanded, are those 

 hydrostatic columns whose pressure affects these subterranean 

 waters from the level of their most elevated sources ? I answer, 

 they must be sought for, even beyond the sphere of vision, at 

 the distance of forty, of eighty, of one hundred and eighty miles, 

 and even more, if necessary. The existence of a watery subter- 

 ranean communication of 300 miles of extent, evidently cannot 

 be a serious objection, except to those who would pretend, in op- 

 position to the testimony of science, that 300 miles of country 

 may not have the same geological constitution. But, in addi- 

 tion to this reasoning, I shall produce a fact which decides the 

 question. 



At the bottom of the ocean, there are springs of fresh water, 

 which are sometimes projected vertically to the very surface. 

 The water of these springs comes evidently from the land, by 

 natural channels, which rise higher than the surface of the sea. 

 A few years ago, Mr Buchanan, a passenger in one of the ships 

 of an English fleet, which was completely becalmed in the In- 

 dian Ocean, discovered an abundant spring of fresh water, at 

 the distance of 123 miles from Chittagong, and of about 100 



