vegetable covering, and the natural face of the earth may be considered
as virtually permanent. 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 Moesia, 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 progress in
fine and mechanical art. 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, 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, indeed, 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 greater quantity, and with much inequality of
distribution; the snow on the summits accumulates for many months in
succession, and then is not unfrequently almost wholly dissolved in a
single thaw, so that the entire precipitation of months is in a few
hours hurried down the flanks of the mountains, and through the ravines
that furrow them; the natural inclination of the surface promotes the
swiftness of the gathering currents of diluvial rain and of melting
snow, which soon acquire an almost irresistible force and power of
removal and transportation; the soil itself is less compact and