420 



Now the last process takes time and it is obvious that the water 

 so used must be delayed in its dreuit : but the chief interest is the 

 rate at which the 60 per cent was run off in the streams. It was 

 run off rapidly from the pasture but slowly from the forest: thus 

 in the springs when the thaw came, the forest allowed the liberated 

 water to escape much more slowly than the pasture: and through 

 the summers when sudden downpours occurred, the stream from 

 the pasture valley for a time would discharge per second twice to 

 thrice as much -water as the stream from the forested valley, for the 

 same fall of rain. In times of protracted rain the discharge per 

 second would be something up to twice as much, the difference 

 growing less, the longer the downpour extended ; this is as one would 

 expect for every soil has a limit of saturation, lieyond which it can 

 retain no more. 



It follows from the way in which the first valley parted slowly 

 with the rain that its forest soil must t)e much more uniformly 

 moist than the pasture soil : but the reason for this is not, as most 

 think, becau;-e the forest covering prevents the sun from reaching 

 the soil ; but is in the circumstance that a forest soil is absolutely 

 different from one more exposed : it possesses properties for instance 

 which it keep.i for a time after the forest is removed, which we refer 

 to when we call it a " virgin soil; " and the most useful of all the 

 properties of virgin soil from a forest is that of holding moisture 

 against the dessicating effects of exposure to the sun. 



Several factors assist in bringing this about. 



There is more humus in a forest soil than in a pasture soil; and 

 the decay of the humus opens it : there are more roots in a forest 

 soil than in a pasture soil; and they open it: and almost certainly 

 there is an entirely different soil fauna, which brings al)out enor- 

 mous differences. Possil)ly other differences could be enumerated; 

 but the result of all is that forest soil has a porosity lacking in 

 exposed soils, cultivate them as we will. 



That the differences ob.ierved in the running off' of the rainfall 

 from his afforested valley and from his deforested pasture valley are 

 due to the nature of the soil Dr. Engler appears to have no doubt. 



The water of the stream from the pasture valley carried more 

 sediment than that from the afforested valley. 



Had the Swiss Institute's experiments been a comi)arison of 

 an afforested valley "with a bared valley, how much greater would 

 the contrasts have been ; and how much more forcefully would the 

 second stream have poured down in flood, carrying the soil with it. 



These Swiss observations have consideralde interest in Malaya, 

 The porosity of a forest soil is well illustrated in the Peninsula 

 by the way in which the peat-lands of Ivukob and other low-lying 

 places shrink if exposed for tlie cultivation of rubber. The steady 

 release of the rainfall by hill forest is pleasantly shown in the early 

 rice crops that the narrow upper ends of the valleys give in Malacca, 

 The consequence of the removal of forest has been obvious enough 

 in the same neighbourlinod where the Kailway lias had to alter its 



