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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 icy winter, its low 

and powerless sun, and its twelve inches of annual rain, must 

necessarily present, in all its phenomena of vegetable and animal life, 

a striking contrast to the exuberant prolificness of New Grenada. It is, 

however, after all, not absolutely the opposite extreme. There are 

certain regions on the surface of the earth that are actually rainless; 

and it is these which present us with the true and real contrast to the 

luxuriant vegetation and teeming life of the country of the Amazon. In 

these rainless regions all is necessarily silence, desolation, and 

death. No plant can grow; no animal can live. Man, too, is forever and 

hopelessly excluded. If the exuberant abundance of animal and vegetable 

life shut him out, in some measure, from regions which an excess of heat 

and moisture render too prolific, the total absence of them still more 

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