48 



FOREST INFLUENCES. 



As to the effect of elevation above sea-level, there are seven stations 

 over 1,900 feet (579 meters) and seven below 500 feet (152 meters). The 

 mean elevation of thetirst set was about 2,100 feet (732 meters), that of 

 the second about 240 feet (9.3 meters). Lintzel was omitted, and ever- 

 green and deciduous trees were about eiiually distributed in the two sets. 

 The reductions were performed for each of these sets separately, and the 

 results are shown in Fig. 5. The differences are a little more marked 

 than in the case of deciduous and evergreen trees. The range is 



Fig. 5.— Difl'erentea of soil teiuiieratiire (woods and open fields). Coniparisou of elevations above 



sea level (If— O). 



noticeably smaller at the higher levels. The forest cover there has a 

 greater cooling effect in summer and a greater warming effect in winter. 

 Its influence in moderating a climate is, consequently, slightly greater. 

 The difference in inthience of young trees and old is also of interest, 

 but the material is scanty. Lintzel is a station among young trees, but 

 there are only seven years of observation (including 1888, the latest on 

 hand at this writing). The curves are given in Fig. 0, and their lack 

 of evenness betrays the brief series of observations from which they 

 were drawn. The surface summer reduction seems very large, and that 

 at 4 feet unusually small, but these results may be due rather to the 

 soil at the station (Lilneburg heath) than to the trees. Dr. Wollny has 



