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INDIANA UNIVERSITY STUDIES 



between forests and precipitation. He uses the forests and preci- 

 pitation of the eastern half of the United States to iUustrate his 

 point. 



Dr. Zon starts his discussion by bringing up the fact that 

 the eastern half of the United States receives its rainfall from the 

 air currents that come from the Gulf of Mexico and the adjoining 

 ocean. He then cites the work of the noted European meteorolo- 

 gist, Professor Bruckner, who has computed the amount of water 

 evaporated from the land surface and the ocean surface, and the 

 amount of water that is returned to the land and the ocean in the 

 form of precipitation, and who has shown that the regions at the 

 peripher}^ of the continents are able to supply seven-ninths of their 

 precipitation by evaporation from their own areas. In other words, 

 the humidity derived from the ocean is precipitated in a narrow 

 strip along the coast and even there consists of only about two- 

 ninths of the precipitation falling in those regions. This being 

 the case, Dr. Zon suggests that the air currents from the gulf region, 

 upon leaving the coast, drop the humidity acquired over the Gulf, 

 and, as they pass farther north gather up a new supply of moisture 

 which will be precipitated farther on. If it were not for the evap- 

 oration taking place on the land, all of the larger continents would 

 have large desert regions at their interior. 



Then Dr. Zon cites the results of the researches of Professor. 

 Henry, in his recent investigations on the effect of forests upon 

 ground waters in level country and the work of Dr. Franz R. von 

 Hohnel, of the Austrian forest experiment station at Mariabrunn, 

 who have shown that a forest area returns a large amount of water 

 to the atmosphere. Then Dr. Zon says: 'The most valuable and 

 complete work on the subject is by Otozky, a Russian geologist 

 and soil physicist, which appeared as a publication of the forest 

 experiment stations. Otozky worked up an enormous amount 

 of observations, both his personal and those furnished him by 

 other people, and did not find a single contradictory fact. His 

 conclusion is that the forest, on account of its excessive transpi- 

 ration, consumes more moisture, all other conditions being equal, 

 than a similar area bare of vegetation or covered with some herb- 

 aceous vegetation.' 



He continues the discussion as follows: Tf the present area 

 occupied by forests in the Atlantic plain and the Appalachian 

 region were instead occupied by a large body of water, no meteor- 

 ologist would hesitate for a moment to admit that the water surface 

 has a perceptible influence upon the humidity of the central states 



