420 



FORESTRY AND IRRIGATION. 



October, 



the eastward it finds a congenial soil 

 and climate, and there reaches its high- 

 est development, both in quality and 

 quantit5^ In a general way the term 

 White Pine Belt, as used in this paper, 

 refers to an irregular belt extending 

 from northeastern Minnesota on the 

 west to the Canadian maritime prov- 

 inces on the east. This main or cen- 

 tral belt includes northern Wisconsin, 

 northern Michigan, portions of Onta- 

 rio, northern New York, and northern 

 New England. There is also, or rather 

 there were twenty years ago, extensive 

 forests of White Pine in western and 

 central Pennsylvania. 



the movement of cyclonic storms, or 

 atmospheric disturbances around the 

 globe. If the region is situated within 

 the tropics, where cyclonic storms are 

 practically unknown, the weather of 

 one day is almost precisely like that of 

 its predecessor, and it is only at infre- 

 quent intervals that a marked change in 

 the weather occurs. In the temperate 

 zones the movement of cyclonic storms 

 keeps the lower strata of the atmosphere 

 in a continual state of agitation. One 

 storm is quickly succeeded by another, 

 and the atmosphere rarely becomes stag- 

 nated. In the white pine belt there are 

 not onh' a large number of storms, but 



CWMATIC DATA FOR DULUTH, MINNESOTA. 



In defining the climate of a place, 

 we are first concerned with the sum 

 total of its atmospheric conditions and 

 the average daily variation of the same. 

 We wish to know about the tempera- 

 ture what is the highest, the lowest, 

 the average ; how much rain falls, how 

 it is distributed, etc. 



Our second inquir}^ concerns itself 

 with the modifying effect of elevation, 

 proximity of the sea or other large 

 body of water, the effects produced by 

 winds blowing across different kinds of 

 surfaces, and how these react upon the 

 atmosphere. 



The weather that is experienced every 

 day in any region depends largely upon 



each class or type of storm brings its 

 own distinctive weather ; thus storms 

 which enter the United States on the 

 coast of Washington and Oregon and 

 move along the northern boundary are 

 preceded by warm southerly winds, in- 

 creasing cloudiness, and rain or snow, 

 according to the season. 



On the other hand, disturbances 

 which move northeasterly up the Ohio 

 Valley are preceded and attended by 

 strong northeasterly winds, relatively 

 cool weather, and rain in the warm sea- 

 son and heavy snow in the cold season, 

 thus insuring frequent periods of cloudy, 

 rainy weather with intervals of bright 

 sunshine. This may be said to be the 



