234 M. Arago on Artesian Wells 



the velocity of the stream would immediately increase in the 

 others. 



These principles, demonstrable by hydrodynamics, apply most 

 readily to the phenomena which now engage our attention. 



Let us admit that the subterranean river which feeds an ar- 

 tesian well, also partially discharges itself into the sea, or into a 

 river affected by the tides, and this by an opening of consider- 

 able dimensions compared with its own size. According to what 

 we have stated above, if this opening be diminished, the pressure 

 will immediately increase in all the points of the natural or arti- 

 ficial channels which are occupied by the waters of the river; 

 the flow by the well will become more rapid ; or, what is the 

 same thing, the level of the water will rise. Thus, then, every 

 one will understand, that the flow of the rising tide immediately 

 above the opening by which a subterranean river discharges it- 

 self, will diminish, by the augmentation of the exterior pressure, 

 the quantity of water which this river Avill supply in a given 

 time. The effect is precisely the same as would result from a 

 diminution of the size of the aperture. The flowing and ebb- 

 ing of the tide, therefore, will produce a corresponding flowing 

 and ebbing in the spring of the well. And such, in a few words, 

 is the explanation of the phenomenon which has been observed 

 at Noyelle and at Fulham. 



Concerning the Temperaltire of t/ie Water of Artesian Wells. 



Of all the scientific questions which have for some years en- 

 gaged the attention of learned men, one of the most curious, 

 beyond doubt, is, whether the globe still maintains any traces of 

 its original heat. Fourier has brought the solution of this great 

 <juestion in natural philosophy to an observation which is suffi- 

 ciently simple ; he has proved, in short, that if the earth received 

 all its heat from the sun, the temperature of its strata would, in 

 every chmate, be the same at all accessible depths, and also, that 

 it would be found equal to the mean temperature of its surface. 

 But the observations which were made in a great number of 

 mines, were at variance with these conclusions. These obser- 

 vations, however, have not brought conviction to every mind. 

 The gallery of a mine presented itself to many imaginations as a 

 sort of laboratory, in which chemical action was unceasingly 



