10 CLIMATE OF MICHIGAN. 



retardation in spring. It may not be improper to add that a fartlier result 

 of this condition of alfairs, recognized by medical men, and also by even 

 temi)orary residents in these regions is, that this comparative equability of 

 climate is decidedly advantageous to persons in feeble health, and especially 

 so during the warm season. 



That the ameliorating influence of the surrounding lakes, and of Lake 

 Michigan especially, should be potent enough to suffice for the growth, fruc- 

 tification, and safe hybernation of such semi-tropical trees as the apricot, 

 nectarine and peach, in as high a latitude as that of Grand Traverse Bay, 

 and possibly farther, may well be deemed surprising. Of the fact, however, 

 there can be no doubt ; and among the apparent reasons for such fact. Are 

 may notice that the waters of this bay are very deep, and that it seldom ever 

 freezes, in winter, before the month of February, while the deepest waters of 

 Lake Michigan, which are understood to be no great distance from the 

 mouth of the bay, remain unfrozen during the entire winter. 



It is also a fact well-known to nautical men, that a current sets northward 

 along the easterly shore of Lake Michigan, doubtless occasioned by the 

 increased influence of prevalent southwesterly winds, upon the waters nearest 

 that shore ; and also that there is a reverse current along the westerly sliore, 

 thus causing a slow but constant transfer of the warmer waters of the south 

 toward the northerly extremity of the lake, and vice versa, much in the 

 same manner as we see, on a far grander scale, the tepid waters of the Gulf 

 of Mexico transmitted by the gulf stream, to soften the climate of north- 

 western Europe. 



The winds coming from the surrounding waters during winter yield their 

 warmth gradu«lly in traversing the land. This gradual shading out of such 

 influence, in passing toward the interior, becomes more clearly manifest upon 

 examination of the isothermals already spoken of. The average summer 

 temperature of the interior of the Lower Peninsula is thus shown to be four 

 degrees higher than that in the immediate vicinity of the lake, while, on the 

 other hand, that of winter is five- degrees lower. The difl;erence between the 

 extreme minima of these two regions is still more striking, this being fully 

 eight degrees lower in the interior. It is obvious, however, that the ameliorat- 

 ing influence of the lakes is decidedly potent, even in the interior of the 

 peninsula, since the average summer temperature, even here, is fully four 

 degrees lower than that of the Mississippi valley, in the same latitude, wliile 

 the average temperature of winter is three degrees higher, and the extreme 

 minimum four degrees higher. 



Messrs. Wheeler and Smith, in Michigan Flora, remark : " Trees like 

 Liriodendrou tulipifera, Asimina triloba, Cercis canadensis, Gleditschia 

 triacanthos, Cornus florida, Ny^a multiflora, and Morus rubra, which belong 

 to Ohio and central Illinois, have crept nortliward, favored by the mild influ- 

 ence of the lake winds, through the central and western part of the Lower 

 Peninsula, often beyond the middle, and the same is true of smaller and less 

 noticeable plants." 



In the more northerly portions of the State, especially of the Lower 

 Peninsula, even the severities of winter are, in same respects, found to min- 

 ister to the success of agricultural operations. In the regions referred to the 

 snow usually covers the ground before the latter becomes frozen, acquiring a 

 very considerable de})th, such thiit the soil remains unfrozen throughout the 

 winter, and even potatoes may be left ungathered with impunity, while 



