4i 



Grand Manitoulin island and a number of smaller 

 islands in the northern part of Lake Huron are formed of 

 the same series of Ordovician and Silurian rocks that 

 appear in the Western Peninsula. These islands must 

 therefore be included in a general sketch of the Palaeozic 

 formations of the region. 



The Palaeozoic — Pre-Cambrian contact extends across 

 the Province of Ontario from near Kingston to the head of 

 Georgian bay. Northward from this point it is hidden 

 under the waters of Lake Huron except for its occasional 

 appearance on some of the islands along the east side of 

 Georgian bay and on the islands between Manitoulin and 

 the north shore of Lake Huron. 



Geology. 



The formations exposed in this district are indicated in 

 the following table: — 



Devonian.. 



Genessee (Chemung.) 

 Hamilton. 

 Onondaga. 

 Oriskany. 



Monroe. 



Salina. 



Guelph. 



Silurian -{Niagara. 



Clinton. 

 Medina. 

 Cataract. 



Ordovician 



Richmond. 



Lorraine 



Eden. 



Utica. 



Collingwood. 



Trenton. 



Black River. 



Lowville. 



The brow of the Niagara cuesta is marked throughout 



its whole extent by a heavy bedded dolomitic limestone — 



he Lockport dolomite. The more or less precipitous face 



