CHANGES OF CLIMATE FROM CLEARING OF FORESTS. 269 



In Minuesota the vfinterof 1872-'73 was long continued, and extremely- 

 cold, with fierce winds without a parallel in the history of the State. 

 The preceding autumn was dry, with slight rain-falls, succeeded by a 

 light fall of snow, and severe freezing of the ground, the frost extending 

 to a depth of three to five feet. This inclement winter was particularly- 

 fatal to fruit-trees. The trees appeared to root-kill, from lack of moist- 

 ure in the soil, as in some instances where the soil was moist, the trees 

 suflered but little. The loss of evergreens in the winter referred to was 

 widespread, and extended through an extensive region in the IsTorthern 

 and Eastern States. In Wisconsin, where the loss was severe, it was 

 noticed that the rain-fall of October and November, 1872, was less than 

 the average, and that the early freezing in December prevented absorp- 

 tion by the soil. This condition continued, with occasional dry thaws, 

 until spring, with most disastrous effects, especially on dry sandy and 

 gravelly soils, while it was much less, if indeed at all, on clay lands, 

 where from the retentive nature of the soil, the roots could not freeze 

 dry.^ 



The real difference in temperature between two places, as shown by a 

 thermometer, may be quite small, while the apparent difference, as 

 judged by our sensation, may be very great. In a dry atmosphere, and 

 exposed to the winds, the perspiration from our bodies is rapid, and its 

 cooling effect may be painfully severe, while in a humid and sheltered 

 situation we would scarcely realize the cold that might be equally great. 

 This relative difference must be the same with all animal life, and the 

 need of shelter for stock against cold drying winds becomes greater as 

 the climate is drier. Passing to the vegetable creation, we find the 

 principle applied to fruit-trees, evergreens, and other trees not of native 

 growth, and not wholly accustomed to the climate, which depend for 

 success quite as much upon shelter as upon goodness of soil. In the 



century, uotes the fact that changes had been observed iu the climate, in proportion 

 as the lands had been cleared. (Tableau du Climat et du Sol des Etats-Unis, 2 vols., 4to, 

 Paris, 1803.) 



Liancourt, another French traveler, notices the belief that the summer heats in 

 Canada were more fervent, and the winters cold more transitory than formerly. 



Dr. Rush records a belief that the springs were colder and the autumns milder than 

 formerly, the rivers breaking up earlier in spring and freezing later, &c. (A^nerican 

 Museum, vi, vii.) 



Thomas Jefferson says that the snows in winter were neither so recent nor so fre- 

 quent as formerly, and sums up with the conclusion that the summers were longer, 

 the autumns later, and the winters shorter and lighter than in former years. These 

 changes upon clearing lands wore not gradual and slow, but quick and sudden, in pro- 

 j)ortion to the extent of cultivation. 



Noah Webster, in an article written in 1799, "on the supposed change in the temper- 

 ature of winter," and revised in 1806, examines a great variety of authorities, ancient 

 and modern,' leading him to the conclusion " that the weather in modern winters is 

 more inconstant than when the earth was covered with wood, at the first settlement 

 of Europeans in the country, that the warm weather of autumn extends further into 

 the winter-months and the cold weather of winter and spring encroaches upon the 

 summer; that the wind being more variable, snow is less permanent, and perhaps the 

 same remark may be applicable to the ice of the rivers. He attributes these changes 

 to the exposure of the ground from clearings, and the greater depth of freezing of 

 the earth in winter, but he did not find evidence that there was any actual diminution 

 of the aggregate amount of cold in winter, however much its distribution among 

 the seasons may have been disturbed. {Collection of Papera on Political, Literary, and 

 Moral Subjects, pp. 119, 162.) 



It is needless to cite from classical authors to prove the annual freezing of the Ty- 

 ber, the ancient rigors of the climate of Gaul, or the inclement winters of Macedon 

 and the Thracian Bosphorus. The vine and the olive are now cultivated in regions once 

 described as scarcely habitable by man. The vine is now raised in Russia as far norfh 

 as 48° 15'. In France it does not thrive beyond 47'^ 30' north latitude. {Aper<^u statis- 

 iique de V Agriculture et St/lviculture et des Pecheries en Exissie. J. Wilson, 1876, p. 11.) 



1 See Transactions of Wisconsin Hort. Soc, 1874, p. 95. 



