Chap. VI] EDAPHIC INFLUENCES IN THE TROPICS 



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combined with great humidity. In addition, in tropical districts with 

 a heavy rainfall, on account of the great abundance and intensity of 

 atmospheric precipitations, the organic products of decomposition are 



.5 « 



drained away to such an extent that many tropical rivers, especially during 

 the rainy season, assume a coffee-brown colour. 



Soil rich in humus, with 8-9 c / o of organic matter, is found within the 



