370 



APPENDIX 



the forest better watered than cultivated ground? To understand the matter rightly 

 it is sufficient to compare the records of the rain gauges installed under the trees at 

 Cinq-Tranchees with those of the instrument established at Amance-la-Bouzule. 



The following table has that object in view by giving the records for the whole period 

 during which they were kept, and also separately for summer and winter and the entire 

 year. 



A comparison between the quantity of rain water which reaches the ground in an 

 open agricultural region on the one hand, and on the other that which reaches the ground 

 in a forest under shelter of the trees. (Summary only is given for the years 1867-1898.) 



* The forest measurements were at Les Cinq-Tranchees and those on agricultural 

 land at Amance-la-Bouzule. 



An examination of the figures demonstrates that the ground of the forest of Haye, at 

 the center, and under cover of its trees, is always better watered than the neighboring 

 plains. The difference is particularly marked in winter; it diminishes in summer by 

 reason of the foliage. In an average year only 82 per cent was collected at Amance-la- 

 Bouzule of the quantity of rain water collected under the trees at Cinq-Tranchees, the 

 proportion being 86.4 per cent for the months from May to October, and 78.7 per cent 

 only for those from September to April. 



The conclusions drawn from the French reports, however, call for a few remarks. 



The forest rain-gauge indicates the loss resulting to the soil, from the adherence of a 

 part of the atmospheric waters to the foliage; all that it receives arrives at the soil intact. 

 It is not the same with the rain gauge installed on a cultivated field. The surface of 

 this field is covered with a thick carpet of grasses or vegetables which retain a consider- 

 able portion of the fallen rain water, and allow it to evaporate in the air exactly as do the 

 leaves of trees. ^^ 



On the other hand the water condensed by contact with the carpet of vegetation has 

 not been measured either; it is true it must be a very small quantity comparatively, 

 because the carpet of vegetation often fails in cultivated fields during autumn and 

 winter. One may infer that this quantity of water is comparable (somewhat less as far 

 as one can judge) to that which is condensed by contact with dead leaves on the forest 

 soil. 



It appears, therefore, that these remarks will further strengthen the conclusions favor- 

 able to the forest, will become, in fact, valuable a fortiori. I'aking into consideration the 

 actual knowledge to hand, it must be admitted the ground covered by forests in leaf 

 receives more water from the atmosphere than ground under cultivation; the difference 

 can be considerable and reach to 20 to 25 per cent of the rainfall in winter, a season which 

 alone supplies infiltrated waters. 



It would appear that the same holds good in the case of pine forests, especially in 



26 It has been calculated (M. Ney, "der Wald imd die Quellen," Tubingen, 1894, p. 30) 

 that the crop of a field of wheat would have a growing surface of 32,370 square yards to 

 the acre, that of an uncultivated field would have 22,006 square yards, that of a field ot 

 clover 27,190, of a field of potatoes 24,876. The surface of a well developed forest ot 

 beech trees of average age would be 39,707 square yards. 



