Cleopatra | Page 2

of the whole scene,
analogous, in some respects, to that which direct and actual vision would afford us, if we
could look down upon it from the eagle's point of view. It is, however, somewhat
humiliating to our pride of intellect to reflect that long-continued philosophical
investigations and learned scientific research are, in such a case as this, after all, in some
sense, only a sort of substitute for wings. A human mind connected with a pair of eagle's
wings would have solved the mystery of Egypt in a week; whereas science, philosophy,
and research, confined to the surface of the ground, have been occupied for twenty
centuries in accomplishing the undertaking.
It is found at last that both the existence of Egypt itself, and its strange insulation in the
midst of boundless tracts of dry and barren sand, depend upon certain remarkable results
of the general laws of rain. The water which is taken up by the atmosphere from the
surface of the sea and of the land by evaporation, falls again, under certain circumstances,
in showers of rain, the frequency and copiousness of which vary very much in different
portions of the earth. As a general principle, rains are much more frequent and abundant
near the equator than in temperate climes, and they grow less and less so as we approach
the poles. This might naturally have been expected; for, under the burning sun of the
equator, the evaporation of water must necessarily go on with immensely greater rapidity
than in the colder zones, and all the water which is taken up must, of course, again come
down.
It is not, however, wholly by the latitude of the region in which the evaporation takes
place that the quantity of rain which falls from the atmosphere is determined; for the
condition on which the falling back, in rain, of the water which has been taken up by
evaporation mainly depends, is the cooling of the atmospheric stratum which contains it;
and this effect is produced in very various ways, and many different causes operate to
modify it. Sometimes the stratum is cooled by being wafted over ranges of mountains,
sometimes by encountering and becoming mingled with cooler currents of air; and
sometimes, again, by being driven in winds toward a higher, and, consequently, cooler
latitude. If, on the other hand, air moves from cold mountains toward warm and sunny
plains, or from higher latitudes to lower, or if, among the various currents into which it
falls, it becomes mixed with air warmer than itself, its capacity for containing vapor in
solution is increased, and, consequently, instead of releasing its hold upon the waters
which it has already in possession, it becomes thirsty for more. It moves over a country,
under these circumstances, as a warm and drying wind. Under a reverse of circumstances
it would have formed drifting mists, or, perhaps, even copious showers of rain.
It will be evident, from these considerations, that the frequency of the showers, and the
quantity of the rain which will fall, in the various regions respectively which the surface
of the earth presents, must depend on the combined influence of many causes, such as the
warmth of the climate, the proximity and the direction of mountains and of seas, the
character of the prevailing winds, and the reflecting qualities of the soil. These and other

similar causes, it is found, do, in fact, produce a vast difference in the quantity of rain
which falls in different regions. In the northern part of South America, where the land is
bordered on every hand by vast tropical seas, which load the hot and thirsty air with
vapor, and where the mighty Cordillera of the Andes rears its icy summits to chill and
precipitate the vapors again, a quantity of rain amounting to more than ten feet in
perpendicular height falls in a year. At St. Petersburg, on the other hand, the quantity thus
falling in a year is but little more than one foot. The immense deluge which pours down
from the clouds in South America would, if the water were to remain where it fell, wholly
submerge and inundate the country. As it is, in flowing off through the valleys to the sea,
the united torrents form the greatest river on the globe--the Amazon; and the vegetation,
stimulated by the heat, and nourished by the abundant and incessant supplies of moisture,
becomes so rank, and loads the earth with such an entangled and matted mass of trunks,
and stems, and twining wreaths and vines, that man is almost excluded from the scene.
The boundless forests become a vast and almost impenetrable jungle, abandoned to wild
beasts, noxious reptiles, and huge and ferocious birds of prey.
Of course, the district of St. Petersburg, with its