330 THE JOURNAL OF GEOLOGY. 



The question of the origin and mutual relations of the Fun- 

 damental Gneiss and the Grenville series is one about which, 

 though much has been written but little is known. Three views 

 may be taken on the matter — 



( I ) The Fundamental Gneiss may be supposed to contain 

 what remains of a primitive crust, penetrated by great masses of 

 igneous rock erupted through it — the whole having been sub- 

 jected to repeated dynamic action.^ The Grenville Series may 

 be an upward continuation or development of the Fundamental 

 Gneiss under altered conditions, marking in the history of the 

 world the transition from those conditions under which a primi- 

 tive crust formed to those in which sedimentation under the 

 present normal conditions took place. It would seem that if the 

 earth originally had a crust on which the first sediments were 

 deposited when the temperature became sufificiently low to per- 

 mit water to condense, that the said water, at a very high tem- 

 perature and under what are to us now inconceivable conditions 

 but little removed from fusion, might give rise to sediments not 

 altogether similar to those formed by the ordinary processes of 

 erosion at the present time. Also that, under the unique condi- 

 tions which must have prevailed at that early time, in the forma- 

 tion of a crust solidification, precipitation and sedimentation 

 might go on to a certain extent concomitantly, and thus no well - 

 defined break could be detected, or would in fact exist, between 

 a primitive crust formed by solidification from a fused magma 

 and the earliest aqueous sediments or deposits. The Funda- 

 mental Gneiss and the Grenville Series might thus, as Logan 

 supposed, form one practically continuous series and represent 

 parts of the original crust, with the first crystalline or clastic 

 sediments deposited on it, the whole penetrated by eruptive 

 rocks and folded up and altered by repeated dynamic action at 

 subsequent periods. 



The general petrographical similarity of the two series, taken 

 in connection with the more varied nature of the Grenville Series, 



^ See also, The Geological History of the North Atlantic, by Sir William Dawson, 

 Presidential Address, B. A. A. S., 1886. 



