468 BOTANY OF LAKE HURON. 



from Port Frank to Clark Point the coast is bold but not precipitous, 

 has an average height of 100 feet above the Lake, and is composed of 

 the brown calcareous clays of the Saugeen division, sometimes visibly 

 underlaid by members of the Coniferous and Tentaculite Formations. 

 Westward from the Lake the country keeps perceptibly rising, and 

 culminates in a ridge, running between the Townships of Tucker- ' 

 smith and Hibberb in County Huron, which rises to the summit- 

 level of 1,050 feet above the sea. The average altitude above Lake 

 Huron is about 222 feet, and above the sea approximately, 900. The 

 superficial deposits of the drift period form the surface of this trian- 

 gular area, and so vast and universal are these accumulations that 

 access to the foundation rocks can only be made along some of the 

 river channels, and at intervals along the margin of the Lake. These 

 deposits have as yet been but imperfectly studied, but the principal 

 facts of their history, so far as is necessary in the present connection, 

 will be given as briefly as possible. They may be sub-divided in 

 ascending oi-der, into : 



1. Erie blue clay. 



2. Saugeen brown clay. 



3. Local deposits of reddisli clay, gravel and sand. 



The lowest of these stratified sediments is the Erie clay. It is 

 more or less calcareous, containing in many instances 30 per cent, of 

 calcium carbonate, and holds nu.merous pebbles and boulders alike of 

 Palseozoic, Huronian and Laiirentian origin. The second division, or 

 that of the Saugeen clay is, along with beds of modified drift, the 

 superficial deposit of the district, and thus demands some considera- 

 tion in a botanical point of view. It is an aggregate of very fine 

 layers of brown calcareous clay, containing but few embedded boulders 

 or pebbles. Its average thickness seems to be about 100 feet, although 

 in a few instances in north Huron, and along the banks of the Saugeen 

 River, between Hanover and Waikerton, it is found as a very thin 

 bed, overlyiag a dejDOsit of fine brown sand, into which at difierent 

 points the clay is pressed in the foi-m of mammillary masses of various ■ 

 sizes. A great portion, however, of this upper deposit of clay is 

 overlaid by beds of caarse gravel and sand, observed capping the 

 ridges of hills which run in a general east and west direction to the 

 vicinity of the Lake. Crossing these ranges of hills almost at right 

 angles, and extending along the western limit of the district, lies a 

 remarkable ridge composed of water- worn gravel and fine sand, whose 



