336 THE JOURNAL OF GEOLOGY. 



detail its stratigraphical position must remain a matter of con- 

 jecture. 



Leaving the Hastings series out of consideration therefore, we 

 have in this Original and Typical Laurentian area two develop- 

 ments of the Laurentian, generally considered as constituting 

 two series, namely the 



Grenville or Upper series, 

 Fundamental, Ottawa, or Lower Gneiss. 



The Evolution of the Area. — In endeavoring to outline the main 

 events in the evolution of this area it will be necessary to extend 

 the limits of our observation somewhat and seek for evidence 

 bearing on the question in other parts of the Protaxis, where we 

 meet with developments of Huronian and various earlier Paleo- 

 zoic strata not found in the typical area itself. 



From the highly contorted condition of the Laurentian rocks 

 of this area as well as from the abundant evidences of dynamic 

 action which they present both in the field and under the micro- 

 scope, it is evident that they have been subjected to great oro- 

 graphic forces, which in very early times threw them up into 

 mountain ranges, probably of great height. Some of the associ- 

 ated eruptive rocks were intruded before these movements began, 

 or while they were in progress and have accordingly been in- 

 fluenced by them, while others, having been intruded later, have 

 not been affected. 



How high these mountains rose cannot of course be de- 

 termined. Bell states that some of the mountains on the Labra- 

 dor coast now rise to a height of from 5,000 to 6,000 feet, while 

 Lieber has estimated that on the coast of Northern Labrador 

 they rise to a height of from 6,000 to 10,000 feet. Along the 

 southern part of the Protaxis, where the country is much lower, 

 notwithstanding the enormous subaerial denudation and glacia- 

 tion which the area has repeatedly undergone, there are many 

 points still rising from 2,500 to 3,500 feet above sea level, while 

 Logan estimated that the average elevation is from 1,500 to 

 1,600 feet. In the Adirondacks, which are but an outlying 

 portion of this area, there are elevations of over 5,400 feet. 



