18 RURAL MICHIGAN 



not east and west, beginning on the upper reaches 

 of the lakes and terminating at interior points near 

 the south boundary of the State. Thus the line for 

 October 10 joins White Pigeon in St. Joseph County 

 close to the Indiana line, and Grand Traverse Bay 

 far to the north a little below the Straits of Mack- 

 inac. St. Johns and Ionia just north of Lansing 

 the capital of the State, normally receive their llrst 

 killing frosts on September 30, as soon as Mackinac 

 Island. Along the soutli shore of Lake Superior, 

 the autumnal frost period is fixed at a progressively 

 earlier date, and is three weeks earlier on the Me- 

 nominee iron range near the Wisconsin boundary 

 than in the copper country many miles to the north. 

 Elevation may have its influence, but undoubtedly 

 the lakes are the decisive factor. 



In the spring conditions in a measure are re- 

 versed. The wintry waters of the lakes retard the 

 approach of warm weather and of the day of the 

 last killing frost. One notes, for example, that the 

 date of the last killing frost in spring is some ten 

 days later on the western shore of the Keweenaw 

 Peninsula than at points on the western shore of 

 the Lower Peninsula; but the delayed frosts of 

 autumn give the copper region a growing period 

 for vegetation of one hundred and twenty to one 

 hundred and forty days, depending on location, 

 and this is as much as can be said of the country 

 north of Saginaw Bay in the Lower Peninsula, and 

 even of some interior points as far south as Ann 

 Arbor. It is a period only ten days shorter than 



