FORESTS AND CLIMATE 329 



water supply for the garrison, this water being contributed partly by 

 " slight showers " and partly by the " steady dripping " just referred to. 

 "Every exposed object/' says Professor Abbe, "contributes its drip." 

 Another case, described by William L. Hall, in the Hawaiian Islands, 

 is that of the collection of the drip from the trees in a region of heavy 

 fog ( ? cloud) in troughs for the use of cattle. In this locality defores- 

 tation would, it is stated, " reduce the productiveness of the plantations, 

 if not ruin them entirely." 



The present writer has several times, during fogs, noted the drip- 

 ping of water from the wires above the sidewalks in his own city. The 

 sidewalks being dry at the time, the drops from each wire made a wet 

 line on the pavements. Again, when steaming through the thick fogs 

 on the Grand Banks of Newfoundland, many of us have seen real, 

 though gentle, showers of rain falling from the wet rigging on to the 

 dry decks. 



In winter, when the moisture freezes on the trees, the branches and 

 twigs may become heavily covered with "frost." Fischbach has noted 

 the fact that in winters of deficient snowfall in the Black Forest, he has 

 several times observed that the frost shaken off of the trees by the wind 

 has made possible the use of sledges for transporting wood. In one 

 single European case, reported by Wilhelm, the amount of " rainfall " 

 resulting from the occurrence of such a frost deposit on trees was not 

 far below .05 inch. 



In this mechanical collection of water particles by a forest, we seem 

 to have a really effective means of increasing the total fall of rain. It 

 is easy to see that if such favorable conditions are often repeated, and 

 where the trees are tall and have many branches, the surface of the 

 ground beneath the forest may easily receive a not inconsiderable supply 

 of moisture. Such action on the part of forests is further aided by the 

 fact that fogs often seem to last longer among trees. Nevertheless, we 

 should remember (1) that the conditions favorable to this particular 

 forest influence are found only locally, especially on forested mountain 

 slopes and tops ; (2) that the increase in the fall of rain is limited to the 

 area covered by the forest itself, and is, therefore, not upon soil used for 

 agriculture; and (3) that in the European observations, above referred 

 to, this particular action of forests was at work, as well as all other for- 

 est influences, yet the results were, as has been seen, uncertain. 



Influence of Forests upon Hail and Other Storms 

 There has been a widespread impression in parts of Europe that 

 hailstorms avoid forests, and that forests serve to break up and to 

 weaken other storms. The evidence on the question of hailstorms is 

 conflicting, but we may say that the popular impression can be explained 

 on the ground that hail naturally does more damage to tender crops 



VOL. LXXXII.— 23. 



