ii SOILS 9 



WIND, SEA AND RIVERS. The Wind, in places, is a fac- Action of 

 tor in the formation of soils, more especially in dry weather Wl 

 when sand and dust are sometimes carried long distances by 

 strong breezes. The wind also carries straw, leaves and 

 other light objects far away and in this manner often adds 

 fertile matter to a poor soil. 



The Rivers are constantly assisting in the formation of Action of 



rivers. 



soils in various ways. In mountainous regions the particles 

 worn off the rocks are carried down to the low-lands mainly 

 by the action of the rivers : and the running waters, espe- 

 cially when in flood, grind down the rocks and stones by 

 rolling them over and against each other. It will be noticed 

 that the stones in the bed of a river are mostly smooth and 

 round owing to this rolling action, the rounding off of the 

 angles being caused by the constant friction or rubbing to- 

 gether. The mud and gravel brought down by slow-flowing Alluvial 

 rivers in times of floods are deposited in the plains or at the 

 bottom of the valleys where they form alluvial soil, while in 

 swift-flowing rivers they are carried out to sea to be spread 

 along the bottom of the ocean. 



THE SEA. In some places the sea is gradually encroach- 

 ing on the land by wearing away the shore by the incessan-t 

 action of the waves, but in other places the reverse happens, 

 for the sea becomes gradually filled up and so in time is 

 turned into dry land. The mud and gravel brought down The sea bed 

 by rivers and glaciers form, as it were, a submarine soil, and dry land. 

 by volcanic and other agencies, this soil has been in places 

 lifted up above the sea to become in time land capable of 

 cultivation. In some parts of the West Indies, the fact 

 that the land has been formerly under the sea is plainly 

 shown by the beds of coral found at some distance from 

 the shore. In Dominica, for instance, which is a volcanic A part of 

 island, there are cliffs and beds of coral two or three formerly* 

 hundred feet above the sea ; and, as coral is built up in " e n ^ er the 

 the sea by a marine animal, it is evident that parts of 



