722 VOLUME OF HIDDEN PLUTONIC ROCKS. [Ch. XXXTV. 



ture that they also are tertiary. Yet these strata are not only associ- 

 ated with trap rocks and volcanic tuffs, but are also altered by a gran- 

 ite consisting of quartz, felspar, and talc. They are traversed, more- 

 over, by dikes of the same granite, and by numerous veins of iron, 

 copper, arsenic, silver, and gold ; all of which can be traced to the 

 underlying granite.* "We have, therefore, strong ground to presume 

 that the plutonic rock here exposed on a large scale in the Chilian 

 Andes is of later date than certain tertiary formations. 



But the theory adopted in this work of the subterranean origin of 

 the hypogene formations would be untenable, if the supposed fact 

 here alluded to, of the appearance of tertiary granite at the surface, 

 was not a rare exception to the general rule. A considerable lapse 

 of time must intervene between the formation of plutonic and meta- 

 morphic rocks in the nether regions, and their emergence at the sur- 

 face. For a long series of subterranean movements must occur before 

 such rock can be uplifted into the atmosphere or the ocean ; and, 

 before they can be rendered visible to man, some strata which previ- 

 ously covered them must usually have been stripped off by denudation. 



"We know that in the Bay of Baise in 1538, in Cutch in 1819, and 

 on several occasions in Peru and Chili, since the commencement of 

 the present century, the permanent upheaval or subsidence of land has 

 been accompanied by the simultaneous emission of lava at one or more 

 points in the same volcanic region. From these and other examples 

 it may be inferred that the rising or sinking of the earth's crust, 

 operations by which sea is converted into land, and land into sea, are 

 a part only of the consequences of subterranean igneous action. It 

 can scarcely be doubted that this action consists, in a great degree, of 

 the baking, and occasionally the liquefaction of rocks, causing them to 

 assume, in some cases a larger, in others a smaller volume than before 

 the application of heat. It consists also in the generation of gases, 

 and their expansion by heat, and the injection of liquid matter into 

 rents formed in superincumbent rocks. The prodigious scale on 

 which these subterranean causes have operated in Sicily since the 

 deposition of the Newer Pliocene strata will be appreciated, when we 

 remember that throughout half the surface of that island such strata 

 are met with, raised to the height of from 50 to that of 2000 and 

 even 3000 feet above the level of the sea. In the same island also the 

 older rocks which are contiguous to these marine tertiary strata must 

 have undergone, within the same period, a similar amount of up- 

 heaval. 



The like observations may be extended to nearly the whole of 

 Europe, for, since the commencement of the Eocene period, the entire 

 European area, including some of the central and very lofty portions 

 of the Alps themselves, as I have elsewhere shown,f has, with the ex- 



* Darwin, pp. 390, 406; second edition, p. 319. 



j See map of Europe and explanation, in " Principles," book 



