138 MUD. 



answer is, Mainly from the detritus of the mountains. 

 There it has two origins. Part of it is glacial, part of it 

 is leaf-mould. In order to feel we have really got to the 

 very bottom of the mud problem and we are nothing 

 if not thorough we must examine in brief these two 

 separate origins. 



The glacier mud is of a very simple nature. It is 

 disintegrated rock, worn small by the enormous mill- 

 stone of ice that rolls slowly over the bed, and deposited 

 in part as ' terminal moraine ' near the summer melting- 

 point. It is the quantity of mud thus produced, and 

 borne down by mountain torrents, that makes the 

 alluvial plains collect so quickly at their base. The 

 mud flats of the world are in large part the wear and 

 tear of the eternal hills under the planing action of the 

 eternal glaciers. 



But let us be just to our friends. A large part is also 

 due to the industrious earth-worm, whose place in nature 

 Darwin first taught us to estimate at its proper worth. 

 For there is much detritus and much first-rate soil even 

 on hills not covered by glaciers. Some of this takes its 

 origin, it is true, from disintegration by wind or rain, but 

 much more is caused by the earth-worm in person. That 

 friend of humanity, so little recognized in his true light, 

 has a habit of drawing down leaves into his subterranean 

 nest, and there eating them up, so as to convert thei 

 remains into vegetable mould in the form of worm-casts. 

 This mould, the most precious of soils, gets dissolved 

 again by the rain, and carried off in solution by the 

 streams to the sea or the lowlands, where it helps to form 

 the future cultivable area. At the same time the earth- 





t, 



; 



>S. 



