EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 57 



region, the coulee or Barre brook to the North beach, Robin brook to the 

 South beach and Lenfesty's brook directly through the rising escarpment of 

 the Bonaventure rocks to the south. 



The general geologic structure presented at Perce is simple in broader 

 features but is very greatly complicated by a breaking down of primary struc- 

 tures. Perce rock and the cliffs which line the shores between the North 

 and South beaches are exemplifications of the original southermost fold of 

 the Devonic series which seems to have formed the southern limb of the 

 geosyncline indicated by Dr Ells. In this series all outcrops stand at 

 the same angle though separated by beach intervals which are in some 

 measure the sites of fault displacements. The attitude of the strata is 

 almost vertical with a dip of So'^-Ss" to the south and the continuity 

 of this an^le from Perce rock, the higfhest member of the scries, to 

 the beds of Cape Canon is not changed except for minor contortions 

 of the strata in the lower members of the series. 



Of this series all the members except the Perce rock are of Siluric age, 

 and we shall briefly consider them in their actual order as massives and 

 their apparent order in the geologic succession from the base up. 



TJie wall bettveen the beaches 



Siluric — Cape Canon massive. This is a series of calcareous and 

 black argillaceous shales considerably disturbed internall)' by slight folds 

 and undulations, thrusts of slight measure which have produced glisten- 

 ing shear faces, veined in all directions, richly jointed and cleaved, 

 but in spite of all these features the vertical attitude of the mass is 

 still apparent with the slight general inclination toward the south. Irre- 

 spective of its undulations it has a sea front of 630 feet and this is an 

 approximate measure of its actual thickness. After repeated search it 

 has revealed no fossils. 



On the summit of Cape Canon the well grassed rock surface slopes 

 deeply landward, then abruptly rises at a distance of about 400 feet from 

 the edge of the cliff and the strata stand u[)right again in a bare dome of 



