94 



FOREST INFLUENCES. 



Here it appears that the deusely wooded Bosnia is 5° or 6° cooler tliau 

 rocky, nearly treeless Herzegovina, and even cooler by 2° or more than 

 the small island of Lissa, which is exposed to the full influence of the 

 Adriatic. 



All this goes to show that in the western part of the old world the 

 presence of large forests has a very sensible influence on the tempera- 

 ture, so much so that the gradual rise of temperature from west to east 

 is almost invariably broken by it. 



Comparisons similar to those of Dr. Woeikoff can- be made along 

 parallels in the United States with results similar in character but not 

 so striking in quantity. 



The writer has made this comparison for the parallels which follow. 

 The data are taken from the annual reports of the Chief Signal Officer.* 

 They are reduced to a common elevation of 1,000 feet above sea level. 

 I^^o reduction is made for latitude, but the stations used are selected not 

 far to the north or south of the chosen latitude. 



Temperatures alo»<j parallel SS"^ N. 



Lati- 

 tude N, 



Lynclil)urg . . 

 Louisville ... 



Cairo 



St. Louis 



Leavenworth 

 Doilire ("ity. . 

 Las Animas . 



37 

 38 

 37 

 39 

 39 

 38 

 38 



Alti- 

 tude. 



Feet. 

 652 

 551 

 359 

 571 

 842 

 2,517 

 3,899 



AnTiual 

 mean 



temper- 

 ature. Mean 



June temperatures. 



57 

 56 

 56 

 54 

 53 

 56 

 58 



o 



73 

 72 

 74 

 72 

 73 

 79 

 80 



Max. 



82 

 82 

 81 

 82 

 83 

 91 

 96 



Min. 



G4 

 64 

 66 

 64 

 63 

 67 

 66 



December temperatures. 



Mean. Max. Min 



40 

 38 

 o7 

 33 

 30 

 34 

 35 



47 

 45 

 44 

 42 

 40 

 47 

 52 



30 

 30 

 29 

 27 

 24 

 26 

 24 



Leaven Avorth lies near the margin of the wooded and treeless district, 

 but in no case are the woods heavy and unbroken. The mean tem- 

 peratures show no unmistakable effect of the woods, but there is an 

 evident difierence in the December temperatures and a still more 

 marked difference in those of June. The difference is most marked in 

 the extremes, as was to be expected. This is most clearly shown in 

 the mean ain[)litudes obtained by taking the minimum from the maxi- 

 mum. The amplitudes for December at stations in the order given in 

 the above table are 17°, 15°, 15°, 15°, | 10°, | 21°, 28°. The change at. 

 the edge of the plains is very noticeable. For June the amplitudes are 

 18°, 18^, loo, 180, I 20°, I 24°, 30°, with the same change as before. 



This coiaparison is not entirely convincing of the effects of forests, 

 because with the change of condition as to trees there is a large change 

 of elevation, so large that the correction for it surpasses by far the dif- 

 ference which may be expected from the action of forests. This 

 difficulty can not be entirely overcome in the American stations, for the 

 plains form an interior table-land, but individual pairs of stations can 



'1885, pp. 82-84, and 1886, pp. 408-411. 



