xl PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



the lateral displacement of rocks and their denudation by water, the 

 series of events would seem endless, and their magnitude not easily 

 to be exaggerated. But it is evident that these superficial mutations 

 are trifling in amount in comparison with revolutions which must 

 have been going on simultaneously in the inferior parts of the earth's 

 crust. The reality of these changes is certam, although their nature 

 may be obscure ; for we can rarely catch even a gHmpse of the subter- 

 ranean products of the eocene, miocene and pliocene epochs, because 

 it requires far more time than the tertiary periods have as yet 

 furnished, to allow the disturbing causes to uplift, depress, and rend 

 open, or for the ocean to denude the incumbent rocks so as to make 

 it possible for an inhabitant of the surface to behold them and appre- 

 ciate their m.agnitude. 



The Alps indeed, where the convulsions have been greatest, reveal 

 to us some monuments of the vast chemical changes and re-arrange- 

 ment of the component elements of rocks which have taken place 

 since the deposition of the eocene strata, and we thus gain some 

 insight mto the nature of the transformation of mineral masses 

 which must have been going on contemporaneously at greater depths. 

 It appears, for example, that in some places granite has been in- 

 truded into the axis of the Alpine chain, and that in other places 

 various granitiform compounds have been formed since the whole 

 nummulitic formation was elaborated beneath the sea. " In passing," 

 says Sir R. Murchison, " from east to west, from the Austrian into 

 the Savoy Alps, the zone of metamorphism widens laterally, from the 

 centre to the flanks of the chain, so as to affect even the younger 

 secondary deposits, and in one or more tracts even the tertiary, some 

 of the strata called flysch being converted into a crystalline state*.'' 

 Instances are also adduced in the Bernese Alps (by the same author) 

 of bands of granite or granitic schists in the midst of the flysch, de- 

 monstrating that the action of heat and vapours, or the causes com- 

 monly called plutonic, have changed even these modem deposits into 

 gneiss, as well as into quartz rock and mica schistf . 



To whatever geological period we may be disposed to assign the 

 first origin or crystallization of the talcose granite and gneiss of Mont 

 Blanc and other parts of the central nucleus of the Alps, we caimot 

 doubt that they broke through the crust and were protruded into 



* Quart. Journ. of Geol. Soc. vol, v. p. 164. t Il>id' vol. v. p. 213. 



