At Anau there are signs that the desertion was due primarily to aridity or to disturbances accompanying such a change.
Dessication, aridity of climate, was fast compelling forest and arboreal mammals to migrate or radically change their habits of life.
As a rule, they are arid because of their altitude; and because of their aridity they are deficient in their power to produce food-stuffs.
The aridity is a resource, however, in the matter of wool, the superior quality of which is due largely to the deficient rainfall.
For that reason many students of aridity pay little attention to temperature, relative humidity, or winds, and simply measure the evaporation from a free water surface in the locality in question.
Where the aridity is intense, this figure may be somewhat low, and in localities of sub-humid conditions, it will undoubtedly be too high.
It is admitted that even such a classification is arbitrary, sincearidity does not alone depend upon the rainfall, and even under such a classification there is an unavoidable overlapping.
Aridity is a condition met and to be overcome upon every continent.
The characteristics of arid id soils increase as the rainfall decreases and other conditions of aridity increase.
Conditions of aridity favor strongly the formation of lime, and since there is very little leaching of the soil by rainfall, the lime accumulates in the soil.
Hence arises that aridity observed in the greater part of the Canary Islands, notwithstanding the considerable height of their mountains, and the mass of clouds which navigators behold incessantly overhanging this archipelago.
Two Labiate shrubs, Plectranthus rugosus and Meriandra strobilifera, are particularly abundant on the slopes between Haripur and Sairi, and strongly mark the aridity of the climate.
As the mountains became more elevated, especially the Sierra Nevada and Cascade ranges, they blocked the prevailing winds from the Pacific Ocean and extensive aridity developed on their leeward side.
It is this extremearidity that necessitates the abundance of bulbous plants in Khorassan, these deposits of nutrition existing even in several of its Compositae.
It is this extreme aridity that gives Khorassan so rich a spring flora, this season being that of rain, of melting of snow, and the ground being well moistened.
But even these were trifling, the aridity of the air being too great as compared with the small extent of Chummums, to allow the deposit of any considerable portion of the moisture it had derived from the ground.
They had the most difficult time at lower elevations where heat and aridityare greatest.
Heat and aridity are the chief factors controlling all Chihuahuan Desert life.
I am conscious in my devotions of a certain aridity of spirit.
Both men had done wonders in the cause of exploration; but the genii of plentiful seasons and bountiful vegetation seems to have been the forerunner of Sir Thomas, whilst a demon of drought and aridity stalked in front of Sturt.
In the trip just narrated he and his companion, Hovell, had arrested the hasty conclusion that was being formed as to the aridity of the interior.
The scene was quite magical and considering the general aridity for a large part of the year, it appeared almost like a phantasm.
Altitude, latitude, and aridity combine to modify vegetation so that in an arid region one notices extraordinary changes often in a single locality.
The aridity of the country generally held them back.
To this result the aridity of the Protestant scholastics who succeeded Luther and Melanchthon, and the frivolity, incompetence and petty despotism of the small German courts, contributed in no slight measure.
In content they differed from such medieval summaries of knowledge as the well-known work of Bartholomew Anglicus, which had been widely used since the 13th century, chiefly by their greater baldness and aridity of statement.
He was especially impressed with the aridity of the country.
In winter there was the disadvantage of snow in the Rockies and in summer were the aridity and heat of the Mohave desert.
He might have learnt from his own experience the aridity of a life which is barren of love.
Time does the rest, time and the aridity of separations.
Gregory at once seized the opportunity thus afforded of examining the upper reaches of this river, from which former explorers had been driven back by the aridity of the country.
After many attempts to penetrate the sand-hill region which confronted him, the heat and ariditycompelled him to turn back.
They are generally regarded as periods of warmth and aridity and, therefore, probably are times of segmentation of the ranges of boreal mammals and hence times exceptionally favorable to the process of speciation.
Interglacial ages were characterized by warmth andaridity as compared to the glacial ages.
We shall have noted this peculiar change to aridity soon after passing the Equator, as before remarked.
At that moment, because I was entering on that state, I was filled with a joy so great, that it has never failed me to this day; and God converted the aridity of my soul into the greatest tenderness.
Then, no effect whatever is produced; it is quickly over, and aridity is the result.
The bottoms are possessed of a light sandy soil, and the uplands are in many places characterized by aridity and barrenness.
For example, the period of aridity suggested by the dip of the dotted line about 300 A.
The semi-aridity of the Great Plains, produced by their position in the lee of the Rocky Mountains, stopped the advance of the Keewatin ice sheet toward the southwest.
Many observers, quite as careful as those who believe in progressive desiccation, point to evidences of aridity in past times in the very regions where the others find proof of moisture.
At the same time in low latitudes and in parts of the continental interior there is a tendency toward diminished rainfall and even toward aridity and the formation of deserts.
At the present time there seems to be no way of determining whether the general tendency is toward aridity or toward glaciation.
This would favor the formation of loess, but it is doubtful whether the aridity would become extreme enough to explain such vast deposits as are found throughout large parts of the Mississippi Basin.
Great aridity now prevails north of the Himalayas and related ranges, and red beds are accumulating in the centers of the great deserts, such as those of the Tarim Basin and the Transcaspian.
If loess was formed during typical inter-glacial epochs, or toward the close of such epochs, profound general aridity must seemingly have prevailed in order to kill off the vegetation and thus enable the wind to pick up sufficient dust.
This seems more likely than that a period of severe aridity before the advance of the ice killed the trees and made a steppe or desert.
In addition there were thousands of acres of desert land in the valley doomed to aridityunless the water supply could be supplemented.
Utah and Nevada contain large areas of sage-brush desert, comprising what is known as the Great Basin, which has no outlet to the sea, and is doomed to aridity by reason of the absence of living streams.
Yet the greater aridity toward the close of the Acheulean stage was probably not such as to prevent the growth of forests along the borders of the streams.
