32 GEOGRAPHICAL CHANGE. 
tion 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 inclination 
of ground be moderate, so that the superficial waters are car- 
ried off without destructive rapidity of flow, and without sud- 
den 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 natu- 
ral face of the earth may be considered as virtually perma- 
nent. These conditions are well exemplified in Ireland, in a 
great part of England, in extensive districts in Germany and 
France, and, fortunately, in an immense proportion of the 
valley of the Mississippi and the basin of the great American 
lakes, as well as in many parts of the continents of South 
America and of Africa, and 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 Britannia, Germania, Pannonia, 
and Meesia, the comparatively inhospitable homes of barbarous 
races, who, in the days of the Ceesars, 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 progress in fine and mechanical art. 
Destructive changes are most frequent in countries of irregu- 
lar and mountainous surface, and in climates where the pre- 
cipitation is confined chiefly to a single season, and where, of 
course, the year is divided into a wet and a dry period, as is the 
case throughout a great part of the Ottoman empire, and, in- 
deed, in a large proportion of the whole Mediterranean basin. 
In mountainous countries various causes combine to expose 
the soil to constant dangers. The rain and snow usually fall in 
ereater quantity, and with much inequality of distribution; the 
snow on the summits accumulates for many months in succes- 
sion, and then is not unfrequently almost wholly dissolved in a 
