MOISTURE ATTRACTED BY MOULD, 65 



underdrained at the depth of 1"^ ,20, iu the mouths of July, August, 

 September, November and December, and but a very trifling quantity 

 in June and October ; in 1868, very little in May and September and 

 none in June, July and August, In 1867 the total precipitation was 

 1066.84 millimetres ; the evaporation, as measured by the difference 

 between rain-fall and drainage, 733.44 millimetres ; in 1868, these 

 quantities were 1032.86 and 755,74 millimetres respectively. 



M. C6zanne remarks in regard to all the observations cited by him, 

 — " In conclusion, and with every allowance for the small quantity of 

 water which is retained by the leaves, the foregoing observations 

 strengthen the conclusion that, under the same measure of rain-fall, 

 the soil of the forest receives and retains notably more water than 

 does uncovered ground. 



Sect, IV, — On Moisture being Attracted from the Atmosphere, or other- 

 ivise retained in the Ground hy Vegetable Mould. 



The meteorological effects of forests are, as has been intimated, 

 somewhat complicated, and the student of these availing himself of 

 my guidance may be beginning to perceive something of the compli- 

 cation in which they are involved ; but thus far the unravelling of 

 different strands has been found to be practicable, and this operation 

 may be carried a little further without difficulty. 



A distinction has been drawn between the effects produced on the 

 ground by the shade from sunshine, and by the shelter from drying 

 winds afforded by trees and forests. It is necessary, further, to 

 distinguish between the effects produced by shade and by vegetable 

 mould, which exists always, in greater or less quantity, in forest soil, 

 in consequence of the decay and decomposition of fallen leaves and 

 and fallen twigs, and broken or decaying rootlets. 



In the soil of a forest there generally exists more moisture than 

 can be attributed to shade, or to shade and shelter combined ; and 

 much of this is attributable to the attraction of moisture manifested 

 by this vegetable mould. 



By a series of simple experiments this fact may be demonstrated, 

 the quantity of moisture determined, and the proportion attributable 

 to each of the effects mentioned approximately ascertained. 



Take the weight of a hundred grains or of a hundred drams, or the 

 weight of a hundred shot of uniform size, of the apparently dry soil 



