296 ORIGIN OF ERUPTIVE AND PRIMARY ROCES. 



argued by the neptunists and plutonists. The question in dispute 

 then, referred to the origin of the undoubtedly intrusive and 

 unstratified rocks, — granite, porphyry, basalt, <fec. So far however 

 as concerns the primitive stratified rocks, Werner and Hutton 

 both regarded them as of sedimentary origin, although they 

 differed as to the state in which they were deposited ; and Hutton 

 alone considered it necessary to explain their crystalline con- 

 dition by the raetamorphic action of heat. Indeed, instead of 

 there being any analogy between the old controversy and the 

 present question, it happens that Hutton, the founder of the 

 plutonic school of former days, was the originator of the theory 

 at present prevailing of the aqueous origin of the primary 

 stratified rocks. 



On the other hand, it is scarcely possible to say who was the 

 author of the igneous theory, although the writings in which 

 it was propounded are of comparatively recent date. Probably 

 among its earliest supporters was Sir H. T. Dela Beche, who 

 thus expresses himself on the subject : — " If we consider our 

 " planet as a cooling mass of matter, the present condition of 

 " its surface being chiefly due to such a loss of its original heat 

 " by long continued radiation into the surrounding space, that 

 u from having been wholly gaseous, then fluid and gaseous, and 

 " subsequently solid, tluid and gaseous, the surface at last became 

 " so reduced in temperature, and so little affected by the remain- 

 " ing internal heat, as to have its temperature chiefly regulated 

 " by the sun, there must have been a time when solid rock was 

 " first formed, and also a time when heated fluids rested upon it. 

 " The latter would be conditions highly favorable to the pro- 

 " duction of crystalline substances, and the slate of the earth's 

 " surface would then be so totally different from that which now 

 " exists, that mineral matter even abraded from any part of the 

 " earth's crust which may have been solid, would be placed under 

 a very different conditions at different periods. We could scarcely 

 " expect that there would not be a mass of crystalline rocks 

 a produced at first, which, however they may vary in minor 

 " points, should still preserve a general character and aspect, the 

 " result of the first changes of fluid into solid matter, crystalline 

 " and sub-crystalline substances prevailing, intermingled with 

 " detrital portions of the same substances, abraded by the move- 

 M ments of the heated and first formed aqueous fluids." * 



• Report on the Geology of Cornwall, &c, p. 32. 



