In 1864 this question of permanency of a country was 

 brought to our attention as follows: 



If the precipitation, whether great or small in amount, be equally 

 distributed through the seasons, so that there are neither torrential rains 

 nor parching droughts, and if, further, the general inclination of ground 

 be moderate, so that the superficial waters are carried off without destruc- 

 tive rapidity of flow, and without sudden accumulation in the channels 

 of natural drainage, there is little danger of the degradation of the soil 

 in consequence of the removal of forest or other vegetable covering, and 

 the natural face of the earth may be considered as substantially perma- 

 nent. These conditions are well exemplified in Ireland, in a great part 



Soil and water losses 



Runoff 



Inf 



Ground Wafer 



Figure 30. 



of England, in extensive districts in Germany and France, and, fortu- 

 nately, in an immense proportion of the valley of the Mississippi and the 

 basin of the great American lakes * * *. 



Destructive changes are most frequent in countries of irregular and 

 mountainous surface, and in climates where the precipitation is confined 

 chiefly to a single season, and where the year is divided into a wet and 

 dry period, as is the case throughout a great part of the Ottoman Empire, 

 and, more or less strictly, the whole Mediterranean Basin. It is partly, 

 though by no means entirely, owing to topographical and climatic causes 



