UNDERGROUND WATERS AS SOCIAL FACTORS. 611 



bottom of stone or contiguous rock." Palissy further sought means 

 for establishing artificial fountains " in imitation of nature and as 

 nearly approaching it as possible, by following the method of the sov- 

 ereign Fountain-maker." He added the profound thought, which lies 

 to-day at the foundation of experimental geology, " It is impossible to 

 imitate Nature in anything, except we first contemplate her effects, 

 and take her for our pattern and example." Hence we understaml 

 why springs are inexhaustible, because they are unceasingly renewed 

 by the play of permanent forces ; they result from a circulation which 

 is in some respects symmetrical with the great aerial circulation of 

 water. 



Violent phenomena, like earthquakes, have certainly the prerogative 

 of exciting the imagination. But other phenomena, though they take 

 place slowly and in silence, are none the less worthy of interest ; of 

 this character are the mechanism and the fruitful action of the subter- 

 ranean waters, of which springs are the exterior manifestation. Aside 

 from their usefulness to man, the importance of the study of them is 

 all the greater in that their work is not alone applicable to the present 

 time. Since the crust of the earth has existed, and during all the 

 periods of its development, the water circulating within it, sometimes 

 at very high temperatures, has produced considerable and varied 

 effects, which have in one way or another durably registered them- 

 selves, and the explanation of which is facilitated by recent experi- 

 ments. It is, in fact, this incessant circulation which has engendered 

 a large number of mineral species. The present functions of under- 

 ground waters will first engage our attention, the examination of 

 their part in the formation of minerals in ancient epochs being re- 

 served for future studies. 



As the course of rivers depends on the exterior contours of the soil, 

 so is the regime of subterranean waters an immediate consequence of 

 the nature and mode of arrangement of the masses through which 

 they move. 



Except for a very thin covering of vegetable soil, which is a kind 

 of epidermis, the crust of the earth is composed of materials to which 

 the name of rocks is applied, even when, like sand and clay, they are 

 of little coherency. All of these masses have been formed successive- 

 ly, during periods of extremely long duration, and in the midst of 

 conditions of which they bear in themselves the characteristic marks. 

 They are veritable monuments, which delineate in their essential 

 traits the successive revolutions of our globe. 



The rocks constituting the greater part of the continents are 

 called stratified, because they are divided into large parallel layers, 

 to which are given the name of strata or beds. It is certain that the 

 rocks of this category, whatever their composition, have been formed 

 in the seas or lakes by sediments and organisms : a sure proof of this 

 truth is furnished by their pebbles and sands, the origin of which can 



