210 M. Arago 07i Artesian Wells 



found that that part of the hill which was on a higher level 

 than the spring, and which consequently might transmit its 

 waters in the way of simple percolation, was nearly 000 

 yards long by about 200 broad, which, according to the mean 

 quantity falling at Paris, would supply a volume of water a 

 great deal larger than the quantity which annually issues from 

 the spring under consideration. The difficulty, therefore, was 

 to be sought for in some other locahty. And it was supposed 

 to be discovered in the neighbourhood of Dijon ; but there also, 

 despite of appearances, it was found that the quantity of rain 

 which fell on the hill above the spring, was more than sufficient 

 for its supply. The Font Feyole, on the celebrated Mont 

 Ventoux, departement deVaucluse, at an elevation of 1754 yards, 

 has also been adduced: but the summit of the mountain is 200 

 yards above it ; and as there has been no accurate comparison 

 between the quantity of rain, dew, and snow, which falls on this 

 portion of Mont Ventoux, and the quantity of water which real- 

 ly issues from Font Feyole, the objection, in its present form, 

 is of no value. But a single remark is sufficient to overthrow all 

 these theoretical speculations, which we have been examining in 

 detail. It is this, that, in the time of severe droughts, nearly 

 every spring becomes less abundant, and a vast number dry up 

 altogether, although such causes can have no influence upon 

 the supposed elevation of central vapours, and their subsequent 

 condensation. 



An accurate observation, therefore, concerning the permeability 

 of certain parts of the crust of the globe, most injudiciously ge- 

 neralized, has been the sole cause of the long prevalence of the 

 theory of Aristotle, Seneca, and Descartes, on the origin of 

 springs in elevated localities. But other ideas, which are alto- 

 gether absurd *, about the annual amount of certain running 



• This word will not appear too strong, when I remark, that in a book of 

 which Newton was the editor, viz. Bernard- Varenius' Geographj-^, and which 

 was the text-book of the students at Cambridge at the close of the 17th cen- 

 tury, these words occur : " Rivers of the largest size contain such a vast 

 quantity of water, that the volume which one of them conveys to the sea ijj 

 a year exceeds that of the whole earth ! ! ! such is the mass which the 

 Wolga empties into the Caspian ; and it is thus absolutely necessary that the 

 water should be incessantly passing from the sea into the earth, &c. ! ! ! " 



