210 EFFECTS OF FORESTS ON SPRINGS AND RIVERS. 



" But it must also be borne in mind that extensive areas of wood- 

 land materially increase the quantity of the rain. At Rohrbrunn 

 (Spessart) 62 per cent, more rain falls than at AschafFenburg, in its 

 immediate neighbourhood, on an average of the years 1867 to 1871- 

 Certainly one-quarter of the gross quantity of the rainfall was caught 

 by the tree-tops and conveyed, by evaporation, again to the atmos- 

 phere, (average of the years 1868 to 1871 at all the meteorological 

 stations.) But of the remaining three quarters of the aggregate rain 

 which fell upon the earth, there evaporated during the same interval 

 six times less from the soil of the forest than from that of the open 

 country ; and, therefore, a much greater quantity of water is absorbed 

 by the forest, where the leaf-litter is retained, penetrating to the 

 deeper strata of the earth, than is held by the soil of the fields. 

 This fact is of the utmost importance in its relation to the formation 

 of springs to the supply of water to the rivers, and to all the 

 numerous interests of agriculture which stand in so close connection 

 with it. 



" The investigations of Ebermayer have also led to very important 

 conclusions in regard to the amount of ozone in the atmosphere. 



" The air contains most ozone in situations of great altitude, 

 where there is much humidity. In dense woods, however, the 

 amount of ozone in the atmosphere is somewhat less than in the 

 directly adjoining open land. The most healthy dwelling-places, 

 therefore, are not in the midst of the forests, but at their borders. 



" The proportion of ozone, on an average, at the six meteorological 

 stations in Bavaria, on the borders of the forest, relatively to that 

 contained in the atmosphere at AschafFenburg and Zwickau, was as 

 follows : 



In spring, as 8-20 : 6-80 : 3-20 

 In summer, as 7-70 : 3-20 : 3-10 

 In autumn, as 8-00 : 5-40 : 2-20 

 In winter, as 8-40 : 6-00 : 1-80 



" These few data satisfactorily demonstrate the general importance 

 to which these forest meteorological stations may lay claim. A con- 

 siderable increase of the number of these observations may soon be 

 expected. 



" To the six stations now existing in Bavaria will shortly be added 

 ten in Prussia, one in Mecklenburg-Schwerin, and three in Alsace- 

 Lorraine. In Bohemia, at PromenhofF, one observatory is already in 

 operation ; also thi-ee in Switzerland, Canton-Berne. The erection of 

 a station at Valambrosa, near Florence, in Italy, is also projected." 



