higher mean temperature. North Africa is much less abundant in corn, and is less graced with tropical vegetation, than in ancient times it was. In the course of two or three thousand years the sand hurricanes of Libya, and of the Sahara, in sweeping over the valley of the Nile, have not only sepulchred its sepulchres, and entombed its temples and palaces in a ten, or twenty, or thirty feet of deposit—narrowing continually the green bordering of the Nile; but they have given dryness for moisture to the neighbouring countries. Dense forests once shed coolness and humidity over large tracts of northern Arabia. The countless millions of people that were subjected to the Assyrian, the Babylonian, the Median despotisms, flourished upon the fatness of the Mesopotamian corn-lands, and by their industry and their water-courses not only preserved the fertility which they created, but rendered the climate itself as temperate as its latitude should make it. Under differing: conditions the same course of physical change has affected Asia Minor—once more populous, in a tenfold proportion, than in modern times these regions have been; for then, population, fertility, mildness of climate, sustained each other.
Those countries of Europe which formed the background of the ancient civilization have, in the course of twenty centuries, been denuded of their forests;—and this is, no doubt, a beneficial change; but this clearance has had great influence in affect-
