THE CLIMATE OF THE LAKE REGION". 227 



These points are the extreme minima of the several local- 

 ities. Now, drawing a line on a map through all the 

 localities which have the sarne extreme minimum, we 

 have an isothermal chart for extreme minima. Its fea- 

 tures are similar to those of a chart of mean minima, 

 but still more pronounced. Here we see the lake influ- 

 ence exerted under its most exaggerated and astonishing 

 aspects. The line of extreme minimum of minus 25, for 

 instance, strikes from Leavenworth, in Kansas, to Ottawa 

 and the vicinity of Chicago; thence along Lake Michigan, 

 a few miles east of Milwaukee, to the immediate vicinity 

 of Mackinac. The isotherm of minus 24 strikes Saint 

 Louis, and passes thence through Central Illinois and In- 

 diana, and thence northward through Michigan at the 

 distance of thirty-five or forty miles from the lake shore 

 to the latitude of Thunder Bay, whence it descends along 

 the eastern slope of the peninsula, and continues south 

 even to the Ohio river. 



To put the facts in a different light, it appears that the 

 lowest point reached at Mackinac in twenty-eight years is 

 but two degrees lower than the extreme minimum of Saint 

 Louis. Extreme weather at Chicago is twelve degrees 

 colder than at New Buffalo. The lowest extreme of Mil- 

 waukee is fourteen degrees below the extreme minimum 

 of Grand Haven, while the extreme of Fort Howard is 

 twenty degrees below that of Northport. In general, while 

 the mean minimum along the west side of Lake Michigan 

 is minus 16, that along the east side is minus 6; while 

 the extreme minimum on the west side is minus 22 to 

 minus 30, that of the east side is minus 10 to minus 

 16 as far north as Little Traverse Bay. On that day of 

 memorable cold, January 1, 1864, the thermometer sank 



