PRECIPITATION OVER WOODS AND OPEN FIELDS. 



109 



"Winter . 

 Spring. . 

 Su:iiiner 

 Autumn 

 Tear . . . 



Halatte, deciduous trees. 



W 



7.44 

 6.90 

 7.11 



8.88 

 30. 33 



O 



7.35 

 6.54 

 6.69 

 7.32 



27.90 



W~-0 



+0.09 

 + 0.36 

 + 0.42 

 + 1.56 

 + 2.43 



Ermenonville, Evergreens. 



IF 



6.11 

 7.47 

 9.25 



7.24 

 30.07 



O 



5.41 

 6.74 

 8.29 

 7.20 

 27.64 



w~o 



+ 0.70 

 +0.73 

 +0.96 

 +0. 04 

 + 2.43 



These results are of so great interest that it is unfortunate that the 

 published series of observations is so short. Kainfall observations, to 

 give satisfactory results, must be derived from a long series of obser- 

 vations. ]M. Fautfat's observations are very consistent among them- 

 selves, however, and the uniformity of signs of W— and the distribu- 

 tion of the values through the season, show that they are not due to 

 accidental limits of heavy rains so arranged as to include oue station 

 and exclude the other. According to these observations, the simple 

 precipitation over woods is 9 per cent more than that over open fields 

 in both cases. The amount which reached the ground under the woods 

 was 90 per cent of that over the fields for one year in the case of the 

 deciduous trees, and this gives the large average percentage of 39 for 

 that which was caught by the foliage. For the evergreen trees and 

 the whole series of observations the amount which reached the ground 

 under trees was only 50 per cent of that in the open, giving here 53 

 per cent as the catch of the trees. The arrangements of rain-gauges 

 by M. Fautrat did not permit the measure of the amount flowing down 

 the trunks. Using the per cent obtained at Cinq-Franchees as the 

 measure of this, we have the following curious and interesting relations 

 between the precipitation over woods, in woods, and outside. The 

 data are percentages of the rain of all outside, in this case at the 

 height of the upper gauge, as that at the lower gauge is not given. 



Deciduous trees 

 Evergreen tree.s 

 Average of two. 



Held by 



the 

 foliage. 



0.31 



0.45 

 0.38 



While Fautrat's observations show that there was a higher rainfall 

 over trees in the department of Oise than over comparative stations in 

 the open fields, they do not show that that occurs in Germany or else- 

 where, but gives enough of a presumption to that effect to make it 

 worth while to examine the subject more fully. It frequently happens 

 at the German stations that the heaviest rainfalls for the month (which 

 are always noted) are greater under trees than at the field station, but 

 as this could easily be due to heavy local rains it is not especially sig- 

 uificaut. It is otherwise with the monthly rainfalls. If the monthly 



