14 GEOLOGICAL AREAS OF CANADA. 



Province boundary line between the Ottawa and the St. Lawrence ; 

 south by the latter river ; and west by a line extending roughly from 

 Brockville to the vicinity of Perth, and from the latter point to the 

 mouth of the Madawaska. Essentially an agricultural region, occu- 

 pied by Lower Silurian formations (ranging from the Potsdam to the 

 Hudson River series), with overlying Glacial, Post-G-lacial, and 

 Recent deposits : the latter represented principally by extensive beds 

 of peat. The average elevation of the district above the sea is from 

 200 to 300 feet. 



(2.) The Gananoque and Back Townships District. — Extends along 

 the St. Lawrence, between Brockville and Kingston, and from these 

 points north-westerly to the north shore of Georgian Bay, thus 

 including the back portions of Frontenac, Addington, Hastings, 

 Peterborough, Victoria, and Simcoe. Essentially a mineral region, 

 occupied by Laurentian strata, composed of gneissoid and micaceous 

 rocks, with beds of crystalline limestone, &c. These, as a rule, are 

 much tilted and broken up, producing a rugged and hilly country, 

 with numerous exposures of bare rock. The district contains im- 

 portant deposits of magnetic and specular iron ore, auriferous mis- 

 pickel, galena, liuor-apatite, marble, &c. Average elevation above 

 the sea, about 800 feet ; but many parts of its area exceed 1,000 feet 

 in altitude. 



(3.) The Lake Ontario District. — Ranges along the entii'e north 

 and west shores of Lake Ontai-io, and extends northwards to the 

 crystalline gneissoid area of the Gananoque and Back Townships 

 District — a chain of small lakes marking more or less continuously 

 the junction of the two areas. In the west, it is bounded by the 

 great Niagara escarpment, which extends from the Niagara River to 

 Georgian Bay. It is essentially an agricultural region, occupied by 

 Lower Silurian strata — rej^resented chiefly by the limestones of the 

 Trenton, the bituminous shales of the Utica, and the shaly sandstones 

 of the Hudson River formations — except in its more western limits 

 where the red marls and sandstones of the Medina formation (of the 

 Middle Silurian series) appear. These formations follow each other 

 in ascending order from east to west, but their strata, apart from the 

 slight dip necessary to effect this, are practically undisturbed. The 

 whole district is more or less overlaid, however, by Glacial boulders, 

 clays, and gravels; Post-Glacial sands, and other deposits holding 

 shells of existing fresh- water moUusca ; and Recent deposits of shell- 



