312 THE KEVOLUTIONS OF THE CRUST OF THE EARTH. 



Mr. Nowak* has proposed a tlieoryof tbe circulatiouof water, which, 

 on account of its singularity deserves to be mentioned. It is based upon 

 some observations made in the Andes by M. Boussiugault. It admits 

 the existence of an envelope of slight thickness which does not rest at 

 all points upon the solid nucleus of the earth, but wbich is lifted up by 

 the vapors proceeding from the waters which iufiltrate it. The mount- 

 ains then are only blisters raised by the force of the vapors which are 

 there condensed. The pressure which these waters of condensation 

 exercise upon the elevated parts of the mountain, produce in these blis- 

 ters — to continue the simile — a species of running wound, origin of the 

 springs, or by sudden action volcanic eruptions, disengagement of va- 

 pors, and the discharge of waters, as this phenomenon is manifested in 

 the 4-ndes. 



It is entirely useless to look for the explanation of these springs in 

 theories based upon problematical data ; while observation demon- 

 strates that the evaporation, the condensation of the vapors, and the cir- 

 culation of the waters in the subterranean canals are sufficient to account 

 for the formation of the springs. This is the opinion of Lyell, and 

 he admits the influence of the central heat upon the production of these 

 phenomena only in the case of thermal springs, the geysers, the mud >vol- 

 canoes and other similar phenomena. 



In this constant circulation the waters dissolve a part of the rocks 

 through which they pass, and, impregnated with salts, return to the sur- 

 face. Pliny observed that the waters are characterized by different 

 properties, according to the nature of the soil through which they pass, 

 and experience show s that, on account of the effect upon fruits and veg- 

 etables, mineral-spring water is unsuitable for culinary purposes, which 

 is not the case with river-water. Instead of explaining this fact by 

 antipathies and sympathies, as the heroic Komans did, chemistry teaches 

 us that selenitic waters hold in solution carbonates of lime, which, in 

 combining with the legumin, render these fruit unfit for alimentation. 



An excess of carbonic a3id facilitates the solution of a notable quantity 

 of calcareous substance, which is deposited in proportion as the carbonic 

 acid is withdrawn. In this way are formed, by the filtration of the waters 

 charged with calcareous substance, the stalactites and the stalagmites 

 of subterranean caves. M. Liebig explains in the following manner 

 the formation of the stalactites. The vegetable materials in decomposi- 

 tion — or humus — under the influence of humidity and of the atmosphere 

 disengage carbonic acid, which is dissolved in the rain-water. This water 

 in traversing the pores of calcareous matter dissolves a part, and, in 

 l^roportion as the excess of acid evaporates in the caverns, the calcareous 

 material is deposited and forms the stalactites. t 



The circulation of the fluids at the surface of the globe is, as we per- 

 ceive, an essential condition of the organization of the terrestrial crust. 



* Die Lehrc rout tcUur'avht)! Dampfe unci ron der Circulaiion (hs Wasscrs iinmrcr J:rde, 

 Prag, 1843. 



t Lyell, Antir[uitij of Man, 16C4, p. 74. 



