558 THE UPPER SILURIAN. 



1. Upper Silurian of Nova Scotia. 



On consulting the map, it will be observed that I have coloured as 

 Upper Silurian certain areas in Cape Breton, more particularly in 

 the eastern and northern parts ; a very irregular hilly tract in Eastern 

 Nova Scotia, commencing at Cape Porcupine and Cape St George, 

 and extending toward the Stewiacke River ; the long narrow band of 

 the Cobequid Mountains ; and a belt of variable width skirting the 

 northern side of the older or Lower Silurian metamorphic district in 

 the western counties. The area occupied by these rocks includes the 

 highest land and the. principal watersheds of Nova Scotia. 



Owing to the alteration and disturbance to which its rocks have 

 been subjected, the structure of this district is much more complicated 

 than that of those which have been described above, and its interior 

 position causes it to present fewer good sections to the geologist. For 

 these reasons less attention has been devoted to it than to the Car- 

 boniferous districts, and the details of its structure are comparatively 

 little known. In describing it, however, I shall endeavour to follow 

 the method previously pursued, by attending somewhat minutely to 

 some of the best and most instructive exposures in coast and river 

 sections, and applying the information obtained from these to the 

 elucidation of the true relations and structure of the remaining portions. 

 I shall then describe the important deposits of useful minerals which 

 occur in this group of rocks, and their fossil remains. In this order 

 of proceeding, it will be convenient to study first the development of 

 the formation in Eastern Nova Scotia, and to proceed westward, 

 returning afterward to the Island of Cape Breton. 



At Cape Porcupine the igneous and metamorphic rocks come boldly 

 out upon the Strait of Canseau, in a precipice 500 feet in height, and 

 afford a good opportunity of studying these rocks and their relations 

 to the Carboniferous system. The central part of Cape Porcupine 

 is a mass of reddish syenite, consisting principally of red felspar and 

 hornblende. This once molten mass passes by gradual changes into 

 hard flinty slates, which, in shattered and contorted layers, lean against 

 its sides, and on these again rest beds of conglomerate, forming the 

 base of the Carboniferous series, and made up of pebbles of syenite 

 and flinty slate, like those of the cape itself. Here we can plainly 

 read the following history : — First, Beds of mud deposited in the sea, 

 probably in the Upper Silurian period. Secondly, These beds upheaved 

 and metamorphosed by the injection of the molten syenite. Thirdly., 

 Large portions of the altered and igneous rock ground up into pebbles 

 by water, and scattered over the sea-bottom .to form the lowest layer 



