THE CLIMATE OF THE LAKE REGION. 225 



the severity of the coldest day, but we may take the 

 average of a series of winters. This is the mean mini- 

 mum. It indicates the lowest temperature which the 

 locality is as likely to experience as to escape. Now, 

 from this point of view, the climate of the lake region 

 stands forth singularly favored. If on a map of the 

 Northwest we draw lines through all the places having 

 the same mean minimum, we shall be surprised to notice 

 to what an extent all the lines are bent northward along 

 the immediate vicinity of the lake. They do not trend 

 east and west, as they must under the normal influence 

 of latitude, but they run literally north and south in the 

 vicinity of Lakes Michigan and Huron. The isotherm of 

 the mean minimum of fifteen degrees below zero strikes 

 from Mackinac through Manitowoc, Milwaukee and New 

 Buffalo, to Fort Riley in Kansas, near the parallel of 39. 

 Here is a deflection of nearly seven degrees of latitude, or 

 about 480 miles in a straight line. The meaning of 

 this is that the most excessive cold at Mackinac, for a 

 period of twenty-eight years, is not, on the average, 

 greater than at Fort Riley, 480 miles farther south. It 

 is one degree less than at Chicago for a term of eleven 

 years. The coldest days of winter are, on an average, 

 no more rigorous at Mackinac than those of Peoria, Illi- 

 nois, or of northern Missouri. If we add to these equal 

 quantities of cold the amount of wind characteristic of 

 each region, it is at once apparent that the balance of 

 sensible and damaging cold turns promptly against the 

 more southern localities. There is no point along the 

 eastei-n shore of Lake Michigan where the mean mini- 

 mum is lower than minus 6. 



One is led to remark, in this connection, the impor- 

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