Since the first advent of white colonists many springs and pans and small streams have dried up, this desiccation being attributed, not so much to decreased rainfall, as to the burning off of the grass every winter, so that the water, instead of soaking in, runs off the hard, baked'ground into the larger rivers.
Possibly the ordinary processes of denudation and erosion, acting on those recent deposits which overlie the harder beds of the older series, may have much to say to these climatic changes, and the wanton destruction of forests may have assisted the efforts of nature; but it is difficult to understand the widespread desiccation of large areas of the Baluch highlands, where evidences of Arab irrigation works and of cultivation still attest to a once flourishing agricultural condition, without appealing to more rapidly destructive principles for the change.
The desiccation of the rivers of Russia has been often attributed to the steady destruction of its forests.
Xxiii.) as to the characteristics of the former flora of the Tianshan, and the changes it has undergone in consequence of the extremely rapid desiccation of Central Asia, must be carefully borne in mind in all speculations founded upon the testimony of language as to the original home of the Aryans.
Many of the great historic movements of peoples were doubtless due to the gradual change of geographical or climatic conditions; and the slow desiccation of Central Asia has been plausibly suggested as the real cause of the peopling of modern Europe and of the medieval wars of the Old World, the theatres of which were critical points on the great natural lines of communication between east and west.
During their removal it is important that the roots be covered, if only to prevent desiccation by the air.
Of the highly developed civilizations which grew up and flourished in Bactria, Bokhara and Samarkand the last survivals are now undergoing rapid obliteration with the simultaneous desiccation of the rivers and lakes.
Everywhere are evidences of water and wind erosion, of desiccation and differential weathering.
In the east, the country of Kanem, the desiccation has been most marked.
The occurrence of characteristic algae at different levels constituting the zones to which reference has already been made, is probably in part an expression of the fact that different species vary in the capacity to resist desiccation from exposure.