UNDERGROUND WATERS. 515 



whicL. it circulated, by vestiges of different kinds wliicli permit 

 lis to reconstitute the various circumstances of its course. 



The external features of an organized being make its constitu- 

 tion known only in an incomplete manner. An adequate anatomi- 

 cal study must penetrate to its interior organs and tissues. Thus, 

 existing thermal springs, even if we take care to scrutinize in the 

 most careful manner the constitution of the country and the con- 

 ditions where they issue, do not suffice to reveal their economy 

 with precision. Their constantly flowing columns of water, even 

 when they are not accompanied with irrespirable gases, prevent 

 our reaching their channels of ascent. In the very exceptional 

 cases in which it is possible to penetrate below their orifices of 

 emergence, as at Bourbonne and Plombi^res, the curious facts 

 which we observe cause us to regret that we can not descend 

 lower. Nature seems to have desired to withdraw from our sight 

 the actual workings of subterranean waters, especially when they 

 are engendering minerals. Water is not more rare than heat 

 in the masses of the interior of the globe. Even when it does 

 not circulate in natural channels, it is at least present, held im- 

 bibed in the most compact rocks. In clays, although combined, 

 it is not less susceptible of acting chemically than in the free 

 condition. Thus, what we have obtained only with many diffi- 

 culties in our experiments, the action of superheated water, is 

 found vigorously exemplified everywhere in the interior of the 

 rocks, where the effective resistance to enormous pressures per- 

 mits the realization of more complete results than are possible 

 with the fragile apparatus of our laboratories. 



The circumstance that heat stored in masses of so little con- 

 ducting power as stony substances is preserved for a very long 

 time, is eminently favorable to chemical combinations and to 

 crystallization. Nature possesses another superior advantage 

 over man in having extremely long lapses of time at her disposal. 

 The importance of this advantage, in the application in which we 

 are now regarding it, appears plainly from what has occurred in 

 the Roman masonry of Plombi^res. Besides this, reactions which 

 go on slowly do not require so high a temperature as those that 

 are of shorter duration. 



The study of waters in their course and effects in ancient 

 epochs thus seems to complete the history and broaden the view 

 of their subterranean works. Here, then, a real exchange of light 

 takes place. The past illuminates the present as much as the 

 present illuminates the past. There is nothing, moreover, to 

 prove that phenomena of this character do not continue down to 

 our own days. We have a right to believe that similar actions 

 are still going on, but in interior regions beyond the reach of our 

 powers of observation. Superheated water, which betrays its ex- 



