126 



FOREST INFLUENCES. 



burg heath, may be recalled, where, with a definite increase in forest 

 conditions over an area of 25 square miles, a regular definite increase 

 in rainfall beyond that of neighboring stations to the extent of 22 per 

 cent within six years was observed, and a change from a deficiency to 

 a considerable excess over the rainfall of these other stations. 



EESULTS OF OBSERVATIONS NEAR NANCY, FRANCE. 



The following observations were made at two stations in the neighbor- 

 hood of Nancy, France. The instruments and their disposition were 

 identical at the different stations. A is a forest station; C, a field sta- 

 tion; B is on the verge of the forest and at a lower level. The follow- 

 ing table gives the amount of raintiill in centimeters for the seven 

 years 18G7, 1868, and 1872, 1873, 1871, 1875, and 187G: 



RESULTS OIVIAINEI) IX I50HKMIA. 



It may also be appropriate here to recall the method by which Dr. 

 Studnicka tried to establish the influence of forest areas upon the dis- 

 tribution of rainl^ill, an account of which I reproduce here from my 

 report for 1888 : 



The latest, most valuable scientific v^ork whicli has been done to decide the impor- 

 tant but dilMcult question of the influence of forests on precipitation is the work of 

 Dr. F. J. Studnicka, professor of jnathematics at the University of Prague, published 

 under the title, "Basis for a Hyetosraphy of Bohemia," in which the results of 

 many years of observation at seven hundred ombromctric stations arc embodied, criti- 

 cal ly sifted, and scientifically considered. The author employs a wholesale method 

 which is quite novel, complying with Woeikoff's idea that it is necessary to reduce 

 the observed data to a common basis for comparison. To understand the sisinificance 

 of these observations an inspection of the map of Bohemia will be desirable, which 

 shows it to be a basin surrounded on all sides by high mountains. 



The work of ombrometric observations, altliongh ])egun in Bohemia during the 

 last century, was neAvly organized in 1879 or 1880, when a systematic net of ombro- 

 metric stations was instituted, and in 1885 and 1886 it was extended to over seven 

 hundred stations, for the purpose of obtaining accurate data of the quantity and 

 distribution of precipitation over the Kingdom. Uniform ombrometers were used 

 and very carefully placed. As at present organized, there is one station for every 75 

 square kilometers (about 30 square miles). No other country, I believe, can boast 

 such a service. Although the time of observation at most stations has been short, 

 and the averages would have been more accur.itely represented by an extension of 

 observations for ten %q twelve years, yet the last four years of observations, for whicU 



