314 MINERALS AND GEOLOGY 



feet above the sea) in a series of ridges or terraces running in a 

 general east and west direction. These ridges are composed of Drift 

 materials, mostly sand and gravels filled with boulders of various 

 kinds, brought down from northern sources during the Glacial and 

 Post-Glacial epochs, by glaciers or by floating icebergs, when the 

 land was necessarily beneath the sea (vide page 207). The highest 

 ridge in Albion and King townships has an elevation of from 700 to 

 750 feet above Lake Ontario, but becomes gradually lower in its east- 

 ern extension. Near the village of Stirling, in Hastings County, it 

 averages 515 feet above the ordinary level of the lake; and a few 

 miles east of this spot it merges into the general levels of the country. 

 Lake Simcoe to the north is 704 feet above the sea, and Balsam Lake 

 (the northern part of which lies within the crystalline area already 

 described) is still higher, its elevation being 820 feet above the sea. 

 Belmont Lake and Rice Lake are each nearly 600 feet, and Scugog 

 Lake (in the midst of the Drift ridges) is nearly 800 feet above the 

 sea level. 



The strata of the District consist essentially of Lower Silurian 

 formations, overlaid extensively by Glacial and Post-Glacial deposits ; 

 but on its extreme eastern border a few indications of the (Upper 

 Cambrian) Potsdam formation have been recognised ; and along its 

 western limits, the (Upper Silurian) Medina and Clinton formations 

 outcrop beneath or upon the great Niagara escarpment, and connect 

 the Lake Ontario District with the Erie and Huron region of the 

 Province. These strata, apart from a few subordinate anticlinals, 

 exhibit a slight inclination only towards the west or south-west; and 

 they are altogether free from intrusions of trappean or other eruptive 

 rocks. In ascending order, and succeeding each other in successive 

 outcrops from east to west, they comprise representatives of the 

 Potsdam, Black River and Trenton, Utica, Hudson River, Medina, 

 and Clinton formations. 



The Potsdam formation is very sparingly represented. It occurs 

 in the form of a thin band (or in broken patches) of sandstone and 

 conglomerate lying along the south-western edge of the crystalline 

 gneissoid region in the townships of Loughborough and Storrington. 

 Exposures occur on Loughborough Lake and on Knowlton and Eel 

 Lakes Some of the beds in Storrington are readily friable, and 

 yield a refractory sand employed as a lining for iron furnaces. The 



