GEOGRAPHICAL CHANGE. 31 



toral state keep down the incipient growth of trees on the half- 

 dried bogs, and prevent them from recovering their primitive 

 condition. 



Young trees in the native forest are sometimes girdled and 

 killed by the smaller rodent quadrupeds, and their growth is 

 checked by birds which feed on the terminal bud ; but these ani- 

 mals, as we shall see, are generally found on the skirts of the 

 wood only, not in its deeper recesses, and hence the mischief they 

 do is not extensive. 



In fine, in countries untrodden by man, the proportions and 

 relative positions of land and water, the atmospheric precipitation 

 and evaporation, the thermometric mean, and the distribution of 

 vegetable and animal life, are maintained by natural compensa- 

 tions, in a state of approximate equihbrium, and are subject to 

 appreciable change only from geological influences so slow in 

 their operation that the geographical conditions may be regarded 

 as substantially constant and immutable. 



Natv/ral Conditions favorahle to Geograj)hicaZ Change. 



There are, nevertheless, certain climatic conditions and certain 

 forms and formations of terrestrial surface, which tend respect- 

 ively to impede and to facilitate the physical degradation both of 

 new countries and of old. 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 incHnation of ground be moderate, so that 

 the superficial waters are carried off without destructive rapidity 

 of flow, and without sudden accumulation in the channels of nat- 

 ural drainage, there is httle danger of the degradation of the soil 

 in consequence of the removal of forest or other vegetable cover- 

 ing, and the natural face of the earth may be considered as virtu- 

 ally permanent. These conditions are well exemplified in Ire- 

 land, in a great part of England, in extensive districts in Ger- 

 many and France, and, fortunately, in an immense proportion of 



abundant in fossil wood that within thirty years they have yielded above a 

 million of trees — shows that the trees have generally fallen from age and not 

 from wind. They are found in depressions on the declivities of which they 

 grew, and they lie with the top lowest, always falling towards the bottom of 

 the valley. —Vaupell, Bogem Indvandnng i de Danske Skove, pp. 10, 14. 



