EOLIAN GEOLOGY 
161 
EOLIAN GEOLOGY 
Physiographic Paradox of the Desert. Fresh from his green 
homeland in pluvial clime the stranger on the desert finds striking 
anomalies abounding on every hand. Everything in nature ap¬ 
pears to be reversed. Seemingly common features easily ex¬ 
plained in the moist country in arid lands are without reason for 
their existence. General leveling and lowering of the land sur¬ 
face manifestly goes on in the desert as fast as in humid tracts 
but without appreciable aid from rains or streams. 
Deserts are strictly climatic productions. They are the areas 
of earth having the smallest precipitation combined with the great¬ 
est evaporation. The notable dearth of plant-growth which give 
them title is merely a necessary consequence of this deficient mois¬ 
ture. In two broad bands arid tracts girdle the earth, on either 
side of the tropics. Deserts are described as lithogenetically equiv¬ 
alent to sea-basins without out-flow. For the development of the 
landscape effects of such regions we now begin to look to the wind 
and not to water for chief graving-tool. 
To one used to only the landscape perspective of humid coun¬ 
tries the desert appears full of paradox. There are copious rains 
which often wet not the soil. Gushing springs exist but they do 
not give rise to water-ways. Babbling mountain brooks are short¬ 
er than their slopes; and they are as discontinuous at their lower 
ends as at their heads. Lakes there are which never overflow their 
basins; they often spring forth in a night; and after a few weeks 
not a trace of them is ever again seen. The few great rivers which 
traverse dry regions receive no lateral augmentation to their waters 
within the boundaries of the arid country; and they are smaller 
when they leave these districts than when they enter them; they 
take no part in the general leveling and lowering of the region; 
they are wanderers in a strange land — perhaps apparitions of a 
bygone age. 
