380 APPENDIX 



account of the fourth congress of the International Association of the "Stations de 

 Recherches Forestieres," which assembled in Austria in September, 1903.^8 



At this congress, M. Hartmann, an engineer of the Bavarian State, gave an account 

 of the results of researches undertaken in collaboration with the Forest Service by the 

 Royal Hydrotechnical Service with a view to the comparative study of the oscillations 

 of the level of the subterranean water in wooded ground or in the open. 



Observations were taken at two points. The first, Mindelheim, at a height of 2,014 

 feet, is situated on almost perfectly horizontal ground at the surface (inclination six per 

 thousand) composed of the alluvial deposits of the Mindel, a direct tributary of the 

 right bank of the Danube. 



The forest is situated in a small piece of isolated ground composed of about 988 acres 

 in the midst of landed estates, and is composed of oak, Scotch, and spruce pines, of about 

 9 years of age. The other station, Wendelstein, is in the neighborhood of Niirnberg. 



M. Hartmann thinks it can be concluded from his statements « that the forest exerts 

 no influence on the level of the subterranean sheet. The latter is generally not stagnant 

 (as has been known for a long time) but takes a more or less rapid course according to 

 the inclination of the surface of the subsoil, the thickness of the subterranean sheet in 

 motion, and the degree of permeability of the soil in which it moves. The considerable 

 differences in the level of subterranean waters observed in Bavaria at points contiguous 

 to a horizontal and homogeneous soil at the surface, can only be explained by the varia- 

 tion in the projection of the subsoil stratum, and by the very variable depth and celerity 

 of the subterranean sheet. 



At Mindelheim, in fact, the subterranean sheet is nearer the surface under the woods 

 than in the open. M. Hartmann thinks that the forest counts for nothing, and that the 

 reverse might just as equally hold good. 



Conclusions. — In the course of this long study on the influence of forests on the 

 feeding of springs, we have particularly insisted on certain points which, recently 

 brought to light, have hitherto only been dealt with in original memoranda, and are 

 therefore inaccessibleto the greater number of readers. 



This chapter, now that its end has been reached, leads to one conclusion. 



(1) We have seen that the forest has the effect of increasing the abundance and the 

 frequency of atmospheric precipitations. 



This action of the forest, proved by many experiments in France and abroad during 

 30 years, must be regarded as a well established fact, although certain authors, without 

 absolutely denying it, have declared it negligible, or else of so slight a nature as not to 

 be ascertained by ordinary rain gauges, since these instruments are lacking in absolute 

 accuracy. 



The increase of water which the forest obtains, amounts to 23 per cent in an average 

 of 33 years of observations taken at the "Station de Recherches" of Nancy. It seems 

 however to increase with the altitude of the place where the forests are situated. 



(2) The forest retains a part of the fallen water by its adherence to the crowns and 

 branches and this returns to the atmosphere by direct evaporation. On the other hand 

 these same crowns and branches are always colder, and often to a very considerable 



^^Vierte Versammlung des internationalen Verbandes forstlicher Versuchsanstaten, 

 1903. Mariabrun, 1904 (published by the "Station de recherches autrichienne"). 



^s It seems to us that the conclusions of the Bavarian engineer are somewhat lacking 

 in precision, at least in the text we have before our eyes. One might conclude, it would 

 seem, especially from the accounts given by himself, that the two points chosen for the 

 experiments were not at all suitable for the purpose, the subterranean sheet being far 

 from immovable, and the subsoil not horizontal. In any case, we find nothing here of a 

 nature to invalidate the very clear and well balanced results of the measurements taken 

 at Moudon, as given us by M. Henry. 



