TROPICAL AGRICULTURE chap. 



Dominica have been in past times below the surface of 

 the ocean. 



Mountain 

 soils. 



Lowland 

 soils. 



The mud. 



Fossil 

 remains 



Distribution of Soils.— We have seen that the soil 

 has been formed for the most part by the gradual wasting 

 away of hard rock, and we now know that the soil thus 

 formed is brought down from the higher land mainly by 

 rivers and glaciers and floods of rain — in other words by 

 water in its ordinary or its frozen condition. Of course a 

 portion of the soil stops on the slopes of the mountains when 

 they are not too steep, but the greater part is carried farther 

 down ; and, as a rule, the finer the soil the farther it is 

 carried. The big stones and rocks broken off by the glaciers 

 — and the various other processes we have been consider- 

 ing — are left behind, and the smaller stones are carried 

 lower down to form gravels, while the fine soil in the shape 

 of mud is carried for long distances and spread over the 

 land as sands and clays. If some mud be taken and stirred 

 in a glass of water and allowed to rest, it will be found 

 after a time that the mud will settle at the bottom of the 

 glass and the water will remain clear on top of it. And this 

 is what occurs, and has occurred since the world was created, 

 in regard to the fine particles of rock brought down by 

 floods, rivers and glaciers from the high lands. The mud 

 has settled on the land and formed the soil that we now 

 cultivate. In order to understand all this, it must be re- 

 membered that the world has not always been what we now 

 find it. The land has altered in shape and elevation, the 

 sea has been over much of the land, and the land of those 

 days is now, in places, under the sea, and the climate of 

 different countries, as we now find it, is quite altered from 

 what it was many years ago. This is shown by the remains 

 of elephants and other animals that live in hot climates 

 being found embedded in the ice of Siberia and other in- 

 tensely cold regions. Unless we remember all these won- 

 derful changes, and think of the thousands of years that have 



