THE CLIMATE OF THE LAKE REGION. 219 



the influence of Lake Huron, it bends southward again 

 and passes into Canada, near the southern extremity of 

 that lake. It passes thence in a northeasterly direction 

 to Penetanguishene, on Georgian Bay. This isothermal 

 is deflected, through the influence of the lakes, to the 

 extent of 5 of latitude, or 350 miles in a straight line. 

 The general course of all the isothermals from 67 to 75 

 is extremely similar to that just traced. 



It follows, from these indications, that an almost 

 identical July temperature stretches along the two shores 

 of Lake Michigan from Chicago to Mackinac. It appears, 

 however, that the immediate western shore is somewhat 

 more cooled than the immediate eastern. This results, 

 as a careful investigation has shown, from a slight pre- 

 ponderance of winds in July from points east of the 

 meridian. At Chicago this preponderance, including north 

 winds, is as 60 to 33; at Milwaukee, as 48 to 37. But 

 at Milwaukee and northward, northerly and even north- 

 westerly winds feel the influence of Green Bay. 



Further inspection of these isothermals discloses the fact 

 that the July temperature of the peninsula of Michigan 

 is about the same as that of the interior of Wisconsin in 

 the same latitudes; but the heat of the Mackinac region 

 is considerably less than that of Wisconsin and Minnesota 

 on the same parallels. This accounts for the popularity 

 of Mackinac as a place of healthful summer resort. On 

 the contrary, the heat of the central and southern portions 

 of the peninsula is equal to that experienced through the 

 northern half of the states of Indiana and Ohio two or 

 three degrees farther south. The July temperature of 

 Marietta, Ohio, is 73, which is the same as that of 

 Flint, and less than that of Grand Rapids, Michigan. 



