THE CLIMATE OF THE LAKE REGION. 215 



ward an equal distance. The isotherm of 49 sweeps 

 from Evanston, near Chicago, to the mouth of the Manis- 

 tee river, a difference, of latitude of 152 miles. The iso- 

 therm of 50 bends from Kensington, south of Chicago, 

 to Grand Rapids, a difference of latitude of 97 miles. 

 The favorable contrast diminishes in the southern portion 

 of the eastern shore, since in November the cold south- 

 westerly winds either miss the lake entirely or are held 

 at a lower temperature by mingling with wind which has 

 not traversed the lake. These statements relate to the 

 mean autumn temperature of the two sides of Lake 

 Michigan. They show that the autumn temperatures 

 along the west side are found on the east side from one 

 to two hundred miles farther north. To put the subject 

 in another light, an investigation of the monthly means 

 on the opposite sides of the lake during autumn shows 

 that the temperature attained at Milwaukee October 15 

 is not reached at Grand Haven until October 20. The 

 Milwaukee temperature of November 15 is only reached 

 at Grand Haven November 23. The Chicago temperature 

 of September 15 is the same as the New Buffalo temper- 

 ature of September 21. These comparisons show that the 

 warm season is lengthened on the east side about six to 

 eight days in the autumn. In 1865 the first killing frost 

 in the Grand Traverse region was December 2; in 1866, 

 November 15 ; in 1867, November 18. These particular 

 facts are cited because they fell under the writer's obser- 

 vation. 



By a singular and happy exception in the prevailing 

 direction of the wind, we find that during the month of 

 May winds from the east of the meridian preponderate. 

 This is shown again from an extensive series of meteor- 



