BESULTS OF COMPARATIVE OBSERVATIONS: BAVARIA. 249 



These results will be found to agree* with those obtained at other 

 stations, and the rule would doubtless apply to all countries and to every 

 period of time.^ 



Effect from removing the litter^ and the result from large clearmgs, upon 

 the moisture of the soil. 



The foregoing statements show how closely related in a country, are 

 its wealth in forests and water (as shown by the great influence of the 

 former), and the litter that covers their surface — to the evaporation 

 and moisture. It therefore need not surprise us, that springs and brooks 

 dry up or flow only periodically, and that the mean height of water in 

 rivers and large streams lessens when large surfaces are cleared up, or 

 that springs flow more abundantly and regularly when, by replanting, 

 the extent of forests is increased. The influence of forests and of litter- 

 covering on the moisture of the soil, founded upon these observations, 

 may be expressed not only in percentages, but we may be allowed to 

 draw conclusions from small to great, as they afl'ord the means for esti- 

 mating the loss of water in the soil, caused by large clearings and the 

 taking off of litter from any given surface. 



These figures apply only to soils capillarily saturated with water — a 

 condition which exists only alter heavy rains. If such a soil is exposed 

 to wind and sunshine, it dries up without receiving, as it did from the 

 apparatus, a full supply from below, to replace that which has been lost. 

 The natural soil is therefore in a less favorable condition for evapora- 

 tion than in the experiments; but we may feel the more satisfied with 

 our data, because the comparisons have been made under similar condi- 

 tions as to saturation, and observations could be made with greater ac- 

 curacy than where the moisture was changeable. Total average evapo- 

 ration in six months is shown by the following table : 



Total evaporation from April to September, inclusive, from a square foot of surface. 



From this it follows, that from an acre of ground the following amount 

 of water was evaporated in six months from saturated soil : 



From open fields, 54,450 cubic feet = 3,403,125 pounds = 1,701.5 tons. 



• Observations made in France by M. Faiitrat, and reported to tbe Academy of 

 Scitrncep, showed that in 1874, in a dense wood of 500 hectares, a rain-gansfe fixed on 

 the top of a large poplar, received mnch more water than one of similar height 300 

 meters beyond the borders of the woods. These experiments, continued two years 

 longer, hwd confirmed the first results; and an instrument placed over the Pinussijlves- 

 tris, in a dense forest, at 1-2 meters elevation, was found to receive 10 per cent, more 

 water than in the fields at the same height. " These results," says the reporter, " show 

 evidently that the pines have the property of condensing the vapors, and this in higher 

 degree than in leaf-woods; the difference in their favor being more than 5 per cent, 

 when compared with observations made over oaks and hornbeams." Hygrometrical 

 observations also showed a considerable excess of moisture within the pine forest, as 

 well as over it, as compared with fields, and that the evaporation under pines was 

 considerably more rapid than in a deciduous forest. These results prove the services 

 of pine woods on heated sands and on soils where a want of water has rendered the 

 surface sterile. In such cases the roots may often reach a humid stratum sufficient 

 for the trees, and the atmosphere receives a portion of this moisture to the benefit of 

 the agricultural regions adjacent. 



