THE ANNUAL MEETING. 161 



Westerly winds cease to predominate only in that month when they cease to 

 be beneficial to Michigan. And yet even in that month they exist whenever 

 the interests of vegetation demand. Not only do westerly winds cease to pre- 

 dominate at the juncture when they cease to be beneficial, but at the same junc- 

 ture the warmer land winds from the east of the meridian become predominant. 

 Both causes accelerate vegetation on the east side of the lake. A study of the 

 means for a series of years, at places on opposite sides of the lake, shows that 

 the temperature of Grand Haven, March loth, is equal to that of Milwaukee 

 March 2dst; that of Grand Haven, April loth, is equal to that of Milwaukee 

 April 24th; that of Grand Haven, May loth, is equal to that of Milwaukee 

 May 28th. Re member that these are not comparisons of single instances ; they 

 are comparisons of the results of many years of accurate instrumental obser- 

 vation. They show that in May, Grand Haven is thirteen days in advance of 

 Milwaukee. Add the thirteen days of growing weather gained in spring to 

 the five days gained in October, and we perceive that the growing season is 

 eighteen days longer at Grand Haven than at Milwaukee. Every practical 

 cultivator knows that eighteen days often make all the difference between a 

 crop well-ripened and perfect, and a crop immature and savorless, if not 

 ruined by an untimely freeze. 



This contrast is the same in kind as exists along the whole length of the 

 two shores; but we find it qualified by two influences. First, the northern 

 portion of the western shore receives a warming influence from northerly winds 

 approaching over Green Bay; but at the same time, the greater expanse of 

 water passed over by westerly and southwesterly winds approaching the Grand 

 Traverse region imparts to that region a greater relative influence than is felt 

 by the Grand Haven region. Secondly, the southern portion of our lake shore 

 is exposed to the unmitigated sweep of southwest winds which, in the north- 

 western States, are often the coldest of all; but, on the contrary, this region 

 receives northwesterly and even north winds which have swept over a vast 

 expanse of lake surface. 



It is not to be supposed that these climatic influences ai*e confined to the 

 immediate shore of Lake Michigan. Undoubtedly, they reach there their 

 greatest development; but the tables which I have compiled, and place 

 before you, and the isothermal charts which I exhibit, demonstrate that the 

 whole of our peninsula receives a similar kind of influence. The President of 

 our local horticultural society will inform you how many car-loads of peaches, 

 grapes and other fruits have been sent out of Ann Arbor during the past sea- 

 son. Nor is it to be assumed that the western borders of our great lakes 

 receive none of their equalizing effects. My own charts show that the north- 

 ward deflection of the winter isothermals begins on the west side of Lake 

 Michigan, many miles from the lake. This is also shown on the climatic 

 chart of Wisconsin, published by Dr. I. A. Lapham, in 18G5. My charts also 

 show that a similar influence is exerted upon our peninsula by lakes Huron, 

 St. Clair and Erie. I include Lake St. Clair, because it is always filled with 

 water of the same temperature, except in the stagnant portions, as that of the 

 great lakes beyond, and never cools down in winter, like a small isolated body 

 of water. Moreover, the Huron peninsula lies in the lee of Saginaw Bay, 

 and is another Michigan on a smaller scale. Thus, also, the south shore of 

 Lakes Erie and Ontario are known to be greatly protected from unseasonable 

 frosts and extreme winters, in spite of the preponderance of westerly winds 

 along those shores. 



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