CAUSES OF PHYSICAL DECAY. 
49 
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 permanent. These condi¬ 
tions are well exemplified in Ireland, in a great part of Eng¬ 
land, in extensive districts in Germany and France, and, for¬ 
tunately, in an immense proportion of the valley of the Missis¬ 
sippi and the basin of the great American lakes, as well as in 
many parts of the continents of South America and of Africa. 
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 a dry period, as is the case 
throughout a great part of the Ottoman empire, and, more or 
iess strictly, the whole Mediterranean basin. It is partly, 
though by no means entirely, owing to topographical and 
climatic causes that the blight, which has smitten the fairest 
and most fertile provinces of Imperial Rome, has spared Bri¬ 
tannia, Germania, Pannonia, and Mcesia, the comparatively 
inhospitable homes of barbarous races, who, in the days of the 
Caesars, were too little advanced in civilized life to possess 
either the power or the will to wage that war against the 
order of nature which seems, hitherto, an almost inseparable 
condition precedent of high social culture, and of great prog¬ 
ress in fine and mechanical art.* 
* In the successive stages of social progress, the most destructive pe¬ 
riods of human action upon nature are the pastoral condition, and that of 
incipient stationary civilization, or, in the newly discovered countries of 
modern geography, the colonial, which corresponds to the era of early 
civilization in older lands. In more advanced states of culture, conservative 
influences make themselves felt; and if highly civilized communities do 
not always restore the works of nature, they at least use a less wasteful 
expenditure than their predecessors in consuming them. 
