Why do the Heavens appear blue?

Because of our looking at the dark vacuity beyond our atmosphere through an illuminated medium.  Were there no atmosphere, it is universally admitted the appearance would be perfectly black, except in the particular direction of the sun, or some other of the heavenly bodies, and since the atmosphere is transparent, this blackness (if such an expression may be used) must be seen through it, only somewhat modified by the rays of light reflected by the atmosphere to the eye, from the direction in which we look.  For this reason, the clearer or more transparent the atmosphere is, the darker is the appearance of the heavens, there being then less light reflected by the atmosphere to the eye.  In the zenith, the appearance is always darker than nearer the horizon; and from the tops of high mountains, the heavens in the zenith appear nearly black.—­Mr. B. Hallowell, in the American Journal of Science and Arts.

Why does the heat of temperature of different parts of the earth vary?

Because of the position of the place with respect to the equator, or rather to the ecliptic, or, more strictly still, with respect to the plane in which the earth revolves around the sun; for on this relation depends the temperature of the place, so far as it is produced, directly, by the influence of the sun.  Maltebrun ascribes to it the following influences:  1, the action of the sun upon the atmosphere:  2, the interior temperature of the globe:  3, the elevation of the earth above the level of the ocean:  4, the general inclination of the surface, and its local exposure:  5, the position of its mountains relatively to the cardinal points:  6, the neighbourhood of great seas, and their relative situation:  7, the geological nature of the soil:  8, the degree of cultivation, and of population, at which a country has arrived:  9, the prevalent winds.

Why are the strata of air upon all mountains of successive coldness?

Because the air does not acquire immediately, by the passage of the solar rays, a considerable degree of heat.  Thus, with the elevation of land, cold may be said to increase in very rapid progression.  Winter continues to reign on the Alps and the Pyrenees, while the flowers of spring are covering the plains of northern France.  This beneficent appointment of Nature considerably increases the number of habitable countries in the torrid zone.  It is probable, that at the back of the flat burning coasts of Guinea, there exist in the centre of Africa, countries which enjoy a delightful temperature; as we see the vernal valley of Quito, situate under the same latitude with the destructive coasts of French Guyana, where the humid heat constantly cherishes the seeds of disease.  On the other hand, it is the continued elevation of the ground, which, in the central parts of Asia, extends the cold region to the 35th parallel of latitude, so that in ascending from Bengal to Thibet, we imagine ourselves in a few days transported from the equator to the pole.—­Maltebrun.