THE AM’S,

9 ,

ho is a cbvellcr in tropical climes, they mitigate the wasting and scorching intensityof the solar beams.

It should also be distinctly remembered, that to the existence of mountains we owethe springs and the rivers indispensable to all life ; and, to a great extent, the rains whichsupply their loss and swell their volume. The intelligent observer, while traversing amountainous country, may readily observe the operation of some eminence, not only incollecting together the clouds of heaven, but in forming them from an atmosphere whichwould appear to be destitute of moisture. And the feelings of which he is consciousmay be shared, in some degree, by all who tarry at home, and will attentively considerthis remarkable process.

A transparent current of air begins to deposit vapour as soon as it approaches thesummit of the mountain, and increases till the whole becomes involved in a cloud aslow down as the relative specific gravities of this vapour and the air will admit. Oftenwill such a cloud appear to bo fixed, though a strong wind is blowing, but, in thisinstance, the vapour which had been precipitated on the windward, is dissolved on theleeward side. The more common result, however, is a progressive addition to thecloudy atmosphere, until the whole sky is obscured, and there is • a plentiful fall ofrain. And when, also, the high land simply attracts the clouds which may bo sailingthrough the air, its influence becomes frequently a source of rain, not merely on itselfalone, but on all the country around.

The transformation would, indeed, be immense, could elevations now arise, amongsome extensive plains on the surface of the globe. As the great, arid, and almostbarren deserts of Asia and Africa require only mountains to render them as luxuriantlyproductive as are the equally extensive plains of South America , so could another MontBlanc, or Chimborazo arise amidst the Great Sahara , that immense and desolate tractwould immediately acquire the elements of fertility. For that stony country, with heroand there some cultivable land, yet literally surrounded by a sea of sand, which, beingagitated by strong easterly winds, appears like the surface of the ocean, and often risesinto the air in the form of sand-spouts, requires only water to effectuate so wondrous atransformation. As the rock of the Great Sahara is that of Cheshire, and the soilessentially the same, so, could water bo distilled on the vast wilderness, by some “ cloud-eapt” eminence, plants would spring up, and a succession of vegetation would make it torival that county of Britain , so long remarkable for the richness of its verdure and theluxuriance of its pastures. In like manner, were the fiat of the Almighty to give riseto mountains, the sands of Africa would equal in fruitfulness, the declivities of the Atlasrange ; the salt plains of the Caspian would bo covered with the wealth of Caucasus;and every desert on the face of the earth become an appropriate and desirable home forman.

It is worthy of remark, that while the atmosphere is in itself neither warm nor cold, ithas the quality of becoming heated by the sun’s rays. The degree of heat thus imparteddepends partly on the length of time during which the solar beams act upon the air,and partly on the degree of its density ; so that the heat is less where the air is rarer,and greater where it is denser. Places which are only raised a little above the level ofthe sea, are much warmer than those which stand some thousand feet higher than itssurface.

As, then, the mountain-range is ascended, places are reached, at length, where theatmosphere is so rare that the low degree of heat imparted to it forbids Avater tocontinue in its fluid state, and it is therefore com-erted into ice, or, if it be in the formof vapour, into suoav. The stratum of air Avherc any such change occurs is called thesnoAv-line, and this is regarded as a natural boundary. It might be supposed that thesnow-line AA’ould be found at precisely the same distance from the earth’s surface at every