470 BOTANY OF LAKE HURON. 



is naturally exposed much, more effectually to the boreal winds from 

 the Muskoka territory than is the district lying along the eastern 

 shore of Lake Huron. These cold winds act as refrigerators on the 

 vaporous atmosphere of the Georgian Bay, and are therefore produc- 

 tive of a supply of snow much more abundant than that found along 

 the immediate coast of Lake Huron. The soil, therefore, undisturbed ' 

 by the varying temperature which affects otber districts further south, 

 seldom freezes to any great extent, and consequently must exert a 

 marked influence upon the vegetation of early spring. Such indeed is 

 found to be the case. The snow remains till late, and when it finally 

 disappears, vegetation bursts out with astonishing rapidity and vigour. 

 Doubtless similar physical causes render the vegetation of the Mus- 

 koka district equally precocious and exuberant ; so that here on the 

 45th parallel of latitude, and before the end of May, may be seen 

 peas, beans and potatoes several inches above the ground. To some 

 what different climatological influences, however, is that region ex- 

 posed which borders on the coast of Lake Huron. Here likewise, 

 the prevailing winds are from the north and north-west, but these 

 are materially modified in temperature in their passage over such a 

 body of water. Lake Huron, with its area of 23,780 square miles, 

 cannot but dispense a degree of moisture to its sliores not to be 

 found in more inland localities, and must consequently exercise an 

 equalizing effect upon the summer and winter temperatures of the 

 atmosphere near the coast-line. Here, however, we find no protect- 

 ing rock-escarpments so congenial to the more nortbern vegetation of 

 the Georgian Bay, but a continuous cliff-liaie of brown clay raised on 

 an average 100 feet ^bove the lake. While, therefore, iii the former 

 area are found on the one hand introduced forms which survive the 

 inclemency of winter under its heavy carpeting of snow, and on the 

 other, herbaceous vegetation delighting in boreal winds and the moist 

 cool crevices of rocks ; — in the latter grow arborescent types, the 

 vitality of whose fruit-bud could only be preserved by an eqiiable 

 and moist atmosphere, and the majority of which are decidedly- 

 southern in range. As corroborative of this conclusion may be cited 

 the fact that in the neighbourhood of our great lakes the isothermal 

 lines tread southward, the curve being considerably more acute on 

 the eastern than on the western shoi-es. In this connection it may 

 be observed that the following introduced trees and shrubs grow and 

 flourish most luxuriantly at Royston Park, Owen Sound : — 



