THE HAMILTON ASSOCIATION. ^^ 



ture be proof of such an origin."* So also Dr. Adams affirms that 

 the indistinct foliation of the fundamental gneiss — a term used to 

 designate the lower portion of Logan's Lower Laurentian, — is not 

 in many cases " a survival of original bedding, but is clearly due to 

 movements in a plastic mass." Of the upper portion of the Lower 

 Laurentian, known as Logan's Grenville series, Dr. Adams appears 

 to think that the crystalline limestones and gneisses, while showing 

 great dynamic action, are in all probability made up in part if not 

 wholly of sedimentary material, often occurring in well defined bands 

 or layers like the strata of later formations. But as regards the so- 

 called Upper Laurentian, which embraces the Anorthosite or Norian 

 series of Logan, his view is that their igneous and intrusive charac- 

 ter is well established ; and that while they frequently show a dis- 

 tinct and often a perfect foliation, they are but eruptive masses which 

 have found their way upward by cutting the rocks of the fundamen- 

 tal gneiss and the Grenville series, in many cases being thrust be- 

 tween the bands or strata of the latter in directions of least resist- 

 ance and having foliation induced in them under pressure while 

 deeply buried and very hot.f The fact is however that there are 

 many points upon which the authorities are not yet agreed, either as 

 regards the origin, age, classification or nomenclature of the older 

 rocks. 



For the present purpose it is enough to be assured that while 

 there are large areas in which eruptive masses of granite and gneiss 

 have penetrated the Huronian rocks and thrown them into folds, 

 proving thus their later age, in general the reverse is the case — the 

 Huronian resting unconformably on the Laurentian and being there- 

 tore of later origin ; that the Cambrian, Silurian and Devonian sys- 

 tems are in regular order more recent than the Huronian ; and that 

 these successive systems of rocks have been built out of the ruins of 

 the underlying ones. 



In the course of secular cooling, it may safely be assumed, the 

 crust of the earth became folded by contraction to form high moun- 

 tains and deep valleys, and when after the lapse of long ages the 

 temperature had fallen to the point at which water might form and 

 accumulate the processes of degradation and upbuilding must have 



* Journal of Geology, vol. i., p. 115. 



t Journal of Geology, vol. i., pp. 328-334, 



