But most deserts of actual nature are not all flat, nor all sandy; they
present a considerable diversity and variety of surface, and their rocks
are often unpleasantly obtrusive to the tender feet of the pedestrian
traveller.
A desert, in fact, is only a place where the weather is always and
uniformly fine. The sand is there merely as what the logicians call, in
their cheerful way, 'a separable accident'; the essential of a desert,
as such, is the absence of vegetation, due to drought. The barometer in
those happy, too happy, regions, always stands at Set Fair. At least, it
would, if barometers commonly grew in the desert, where, however, in the
present condition of science, they are rarely found. It is this dryness
of the air, and this alone, that makes a desert; all the rest, like the
camels, the sphinx, the skeleton, and the pyramid, is only thrown in to
complete the picture.
Now the first question that occurs to the inquiring mind--which is but a
graceful periphrasis for the present writer--when it comes to examine in
detail the peculiarities of deserts is just this: Why are there places
on the earth's surface on which rain never falls? What makes it so
uncommonly dry in Sahara when it's so unpleasantly wet and so
unnecessarily foggy in this realm of England? And the obvious answer is,
of course, that deserts exist only in those parts of the world where the
run of mountain ranges, prevalent winds, and ocean currents conspire to
render the average rainfall as small as possible.
Pages:
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412