and Spouting Fountains. '209 



summer do not penetrate above six inches. Lahire also has ob- 

 served, that, in soils covered with vegetation, they, on no occa- 

 sion, penetrate more than two feet ; and he has likewise stated, 

 concerning a bed of naked earth eight feet thick, that not a 

 drop of water had penetrated to the leaden plate which sup- 

 ported it, during the fifteen years it had been freely exposed to 

 every atmospheric vicissitude. BufFon has supplied the results 

 of a similar experiment ; for he mentions having examined, in 

 a garden, a bed of earth more than nine feet high, which had 

 been undisturbed for many years, and he noticed that the rain 

 had never penetrated above four feet deep. 



These several observations would be of the deepest import in 

 the question concerning the origin of fountains, if the surface of 

 the globe were universally covered by a layer of vegetable earth 

 of the thickness of two or three yards. But the very reverse of 

 this is the fact ; and every one knows that, in many places, the 

 superior layer is sand, and that sand allows water to percolate, as 

 if it were a sieve ; whilst in other places the naked rocks appear, 

 and through their fissures and gaps the water runs most freely. 

 In proof of this last assertion, we may state the constant obser- 

 vations of miners, and more especially of those of Cornwall, that 

 in those mines that are situated in limestone, the water increases 

 in the deepest galleries afeii) hours after it has begun to rain 

 above ground. We may also add, that the springs which is- 

 sue at various elevations from the cliffs of chalk on our coasts, 

 are much increased immediately after rain. 



The consideration upon which those who imagine they must 

 look to evaporation and precipitation of subterranean waters, 

 especially on their approximation to the colder strata near 

 the surface, principally take their stand, is one well worthy 

 of examination ; it is the allegation of the existence of co- 

 pious springs at the very summit of certain mountains. Mont- 

 martre, in the neighbourhood of Paris, has borne a'part in this 

 controversy ; for on it there was, and perhaps there still is, a 

 spring which was not above fifty feet below the highest part of 

 the hill. It was maintained that the supply which constantly 

 fed a spring so situated, could only come from beneath ii) the 

 state of vapour. Upon minute examination, however, it was 



