ORIGIN OF CRYSTALLINE EOCKS. 21 



I. Endoplutonic. This supposes the rocks in question to have been formed from the 

 mass of the primeval globe as it congealed from' igneous fusion and, as Naumauu remarks, 

 implies a solidification from without inwards. The process beginning before the precipi- 

 tation of water on the surface, this liquid took no part in their formation, and their strati- 

 form structure and arrangement are to be ascribed to crystallization, or to the effect of 

 currents set up in the congealing mass. (Naumann, T. Macfarlane, Hébert et. al.) 



IL ExoPLUTONic. This hypothesis conceives the crystalline stratiform rocks to have 

 been built up out of matters ejected from beneath the superficial crust of the earth. 

 Besides lavas and pyroclastic rocks, which are the ordinary products of volcanoes, the 

 hypothesis of the Huttonians (in which the notion of metamorphism is carried back in- 

 definitely, so that its products are confounded with the primeval crust,) has apparently led 

 the way to a belief in the eruption not only of re-fused rediments, but of hydrated serpen- 

 tinic and feldspathic magmas, and even, as we have seen, of quartz, magnetite, limestone, 

 rock-salt, anhydrite, and of clays and sands. It would not probably be maintained by its 

 advocates that the eruption of all of these rocks was attended with volcanic phenomena, 

 properly so-called. Such extruded rocks, though not truly volcanic, would however, as 

 coming up from the underworld, merit the more comprehensive designation of exoplutonic, 

 here proposed. 



III. Metamorphic or plutonic-detrital. This hypothesis conceives the crystalline 

 rocks to have been formed by consolidation and recrystallization of sediments arranged 

 beneath the sea, and derived (1) from the ruins of endoplutonic rocks resembling these, 

 (Hutton, and his followers, Playfair, Scrope, Bovie, Lyell, and Dana in ISeS-lSYO) ; (2) from 

 exoplutonic or volcanic rocks, broken up, for the most part, during the process of eruption, 

 which was often submarine. With these materials may also be associated lava-flows. 

 (Dana in 1843, Kopp, Reusch, Tornebohm, Marr, C. H. Hitchcock). The heat, which 

 was believed to effect the metamorphosis of these detrital materials beneath the sea into 

 crystalline rocks, is supposed by the Huttonians to have come from the heated interior by 

 conduction, but, according to the volcanic-detrital hypothesis of Dana, through the direct 

 heating of the waters of the sea by contact with the eruptive matters. 



IV. Metasomatic. Although the crystalline rocks believed to be formed in each one 

 of the preceding methods have been supposed to be occasionally the subject of wide- 

 spread metasomatosis, we may properly restrict the title of a general metasomatic hypo- 

 thesis to that which seeks to explain the derivation of the principal crystalline silicated 

 rocks from limestones, as suggested by Rose, Volger, Bischof and Pumpelly. 



V. Chaotic. We have already suggested the name of the chaotic hypothesis for that 

 which supposes the crystalline stratiform rocks, as well as the granites underlying them, 

 to have been successively deposited by crystallization from a general chaotic ocean, by 

 which their elements were originally held in solution. In this doctrine, which was taught 

 by Werner and his immediate disciples, the conception of internal heat was not recognized, 

 and there w^as no suggestion of an elevated temperature in the chaotic ocean. 



VI. Thermochaotic. The history of the attempts to adapt the Wernerian hypo- 

 thesis to the conception of a cooling globe has already been told in the preceding pages. 

 It was supposed that the waters of the universal chaotic ocean were highly heated, and 

 were thus enabled to exert a powerful solvent action upon the i)reviously-formed plutonic 

 rocks of the primitive crust, transforming them into the present crystalline stratiform 



