OEIGIN OP CEYSTALLINE BOOKS. 11 



neither eruptive nor sedimentary, but is due to a third mode of formation which, borrow- 

 ing the name from d'Omalius d'Halloy, we may call cri/stallophyllian." " It is difficult to 

 conceive that this can be any other than that imagined by Naumann, which we have called 

 endoplutonic. 



§ 23. Thomas Macfarlaue, in a learned essay in 1864, on "The Origin of Eruptive and 

 Primary Eocks," '^^ has developed the hypothesis of the endoplutonic origin of the primitive 

 rocks with much ingenuity, and defends a view already suggested by Scheerer, that the 

 laminated structure of these rocks may have been caused by currents in the molten mass 

 of the globe. He further suggests that the first-formed crust may have had a different 

 rate of rotation from the liquid below ;'"' from which also would result a stratiform arrange- 

 ment in the elements of the solidifying layer, such as is seen in many slags, and in certain 

 eruptive rocks. But while he applies this view to the primitive rocks, he proposes for 

 the later crystalline schists one which is essentially the thermochaotic hypothesis of 

 Delabeche and Daubrée, ascribing their origin to the action of a highly heated primeval 

 ocean on the previously formed crust. The chief difficulties with which this endoplu- 

 tonic hypothesis has to contend, according to Naumann, " arise from the structural rela- 

 tions of the primitive series, and the mineralogical characters of certain rocks belonging to 

 it. Whether these difficulties can be explained away by the supposition of a hydro- 

 pyrogenous development of the outside of the first solidified crust, as indicated by Angelot, 

 Rozet, Fournet, Scheerer and others, we must leave undecided in the meantime." Such 

 a hydro-pyrogenous process is more clearly defined by Daubrée, when he refers the 

 formation of granites and crystalline schists " to aqueous action interA^ening under 

 extreme conditions^ which approach igneous action," as explained in § 14. Any modifica- 

 tions of the heated crust through the intervention of water must come under the 

 categories of what we have called the thermochaotic and the metasomatic hypotheses, or 

 else of that one which remains to be described in the present essay. 



§ 24. In the paper already cited, Macfarlane has, moreover, discussed at length the 

 probable condition of the earth's interior, beneath the crust of primitive stratiform rocks, 

 with especial reference to the origin of the différent tyf)es of eruptive rocks. Already, in 

 the last century, we find Dolomieu maintaining the existence, beneath the granitic substra- 

 tum, of a liquid layer, from which come what he called basaltic lava-flows. A similar 

 view was developed later by Phillips, Du.rocher, Bunsen and Streng, who have imag- 

 ined a separation of the liquid matter at the surface of the cooling globe into two layers, an 

 iipper acidic one, corresponding to granites and trachytes, in which, besides alumina 

 and an excess of silica, lime, magnesia and ii"ou-oxyd are present in very small quantities, 

 and potash and soda abound ; and a lower basic one, corresponding to dolerite and basalt, 

 in which lime, magnesia and iron-oxyd abound, with an excess of alumina, and but 

 little alkali. These two constitute the trachytic and pyroxeuic magmas of Bunsen, who 



" Bull. Soc. Géol. de France (3) xi. 30. 



'' Canadian Naturalist, volume viii. 



" It is worthy of note in this connection that Halley was long ago led, from the study of terrestrial magnetism, 

 to adopta similar hypothesis with regard to the earth's interior. " He supposed the existence of two magnetic poles 

 situated in the earth's outer crust, and two others in an interior mass, separated from the solid envelope by a 

 fluid medium, and revolving by a very small degree slower than the outer crust. The same conclusion was subse- 

 quently adopted by Hansteen." (Hunt, Chem. and Geol. Essays, p. GO.) 



