A remarkable change takes place in the character of heat in being reflected from material substances. In nature we often see this fact curiously illustrated. Snow which lies near the trunks of trees or wooden poles melts much quicker than that which is at a distance from them, the sun shining equally on both--the liquefaction commencing on the side facing the sun, and gradually extending. We see, therefore, that the direct rays of solar heat produce less effect upon the snow than those which are radiated from coloured surfaces. By numerous experiments, it has been shown that these secondary radiations are more abundantly absorbed by snow or white bodies than the direct solar rays themselves. Here is one of the many very curious evidences, which science lays open to us, of the intimate connection between the most ethereal and the grosser forms of matter. Heat, by touching the earth, becomes more earth-like. The subtile principle which, like the spirit of superstition, has the power of passing, unfelt, through the crystal mass, is robbed of its might by embracing the things of earth; and although it still retains the evidences of its refined origin, its movements are shackled as by a clog of clay, and its wings are heavy with the dust of this rolling ball. It has, however, acquired new properties, which fit it for the requirements of creation, and by which its great tasks are facilitated. Matter and heat unite in a common bond, and, harmoniously pursuing the necessities of some universal law, the result is the extension of beautiful forms in every kingdom of nature. An easy experiment pleasingly illustrates this remarkable change. If a blackened card is placed upon snow or ice in the sunshine, the frozen mass underneath it will be gradually thawed, and the card sink into it, while that by which it is surrounded, although exposed to the full power of solar heat, is but little disturbed. If, however, we reflect the sun’s rays from a metal surface, an exactly contrary result takes place; the uncovered parts are the first to melt, and the blackened card stands high above the surrounding portion. The evidences of science all indicate the sun as the source, not only of that heat which we receive directly through our atmosphere, but even of that which has been stored by our planet, and which we can, by several methods, develope. We have not to inquire if the earth was ever an intensely heated sphere;--this concerns not our question; as we should, even were this admitted, still have to speculate on the origin--the primitive source of this caloric. Before, however, we proceed to the examination of the phenomena of terrestrial heat, a few of the great results of the laws of radiation and convection claim our attention.