382 PROCEEDINGS OF OTTAWA MEETING. 



circulation of these waters he imagined these cletrital accumulations to 

 have been differentiated into two great divisions, the one having an 

 excess of silica, a predominance of potash and small amounts of lime, 

 magnesia and soda, represented by the granites and trachytes ; the other, 

 having less silica and potash, and prevalence of soda, lime and magnesia, 

 giving vise to pyroxene and triclinic feldspars. In the metamorphism 

 and displacement of these differentiated sediments he explained the 

 origin of the plutonic rocks. At this period he was a believer in the 

 metamorphic origin of the crystalline rocks, holding with Keferstein 

 "that all the unstratiiied rocks from granite to lava are products of the 

 transformation of sedimentary strata, in part very recent." l'.ut the inti- 

 mate relation, required by his growing hypothesis, between this meta- 

 morphism and the chemical processes acting upon a recently solidified 

 globe, seem to have soon caused him to reject the possibility of the for- 

 mation of crystalline rocks by metamorphic processes acting upon sedi- 

 ments of later than pre-Cambrian age; for, in the final formulation of 

 the crenitic hypothesis, he states that the products of subaerial decay 

 (both of the crenitic rocks and of the basic rocks erupted from the 

 underlying residual primary basic mass), reacted upon by the materials 

 brought up by the crenitic processes, contributed to the formation of the 

 transition crystalline schist, and in the transition or pre-Cambrian schists 

 he saw only the relatively feeble and dying-out action of the crenitic 

 processes. 



It was a natural consequence of this attitude that Dr Hunt took an 

 active part in the " Taconic Controversy " and ranged himself on the 

 side which claimed a pre-Cambrian age for the quartzite limestone and 

 schist series of the great Appalachian valley called Lower Taconic by 

 Emmons and Taconian by Hunt. He had thought out a, system which 

 premises that ''the laws which have presided over the differentiation of 

 the primeval chaos and produced the various groups of rocks, * * :;: 

 which have determined the progressive changes in chemical constitution 

 from the anti-gneissic granite down to the youngest crystalline schists 

 and the detrital sediments of later times, are * * * not less cer- 

 tain and definite than those which preside over astronomical and bio- 

 logical development." He insists that '•the great successive groups of 

 stratiform crystalline rocks mark necessary stages in the mineralogical 

 evolution of the planet.' 1 



Acting upon this idea, he divided the crystalline-rock-making time 

 into six periods : 



I.' Laurentian — granite and gneiss — during which the lixiviating 

 process brought up acid silicates and quartz; the presence of lime- 

 stones in supposed Laurentian rocks being due to a reaction of the 

 crenitic lime silicates. 



