Solar Heat.

Selected writings of A. Jackson Howe.

Professor Howe was equally at home in any of the branches of the natural sciences. He prepared and read many papers before the Cincinnati Society of Natural History on anatomical, physical, astronomical, and geographical subjects—papers which were interesting and instructive because of their richness in facts and clearness of expression. The average listener, whether or not versed in the subject discussed, could fully comprehend the topics presented by Professor Howe in these papers. Aside from their literary value, there is a wealth of material in these articles that makes one regret that they are not all published in a single volume that they may be accessible to the general reader who has not access to the large number of journals in which they originally appeared. This article is a portion only of a paper on "Matter and Energy," read before the Natural History Society, and republished in Howe's "Miscellaneous Papers."—Ed. Gleaner.

SOLAR HEAT.—The internal heat of the earth is no longer competent to warm its crust sufficiently for biogenic purposes. While in a nebulous state there was heat in abundance, but as the gaseous substance became condensed the heat in its molecules was driven out and radiated into space. To counterbalance the loss, an atmosphere was evolved from the environment of ethereal matter. Oxygen and nitrogen held such affinities for one another that air became an envelope for the new-born earth. This had so many intermixtures that it was not "pure" and respirable, but time acted as a clarifier. It was thin and tenuous at its outer boundaries, but denser near the earth. This atmospherical envelope renders organic life possible, and serves as a medium for floating clouds. Birds sustain themselves in flight through the density of the agent. Its pressure upon the earth is fifteen pounds to the square inch at the sea level, but much more rarified at the altitude of the highest mountains. The air is an important agency in the evolution of mundane affairs. While the elastic and vibratile body transmits sound and light with seeming facility, yet it offers more or less resistance to the passage of solar rays. Fortunately this friction becomes a source of heat, as in a revolving axle or in any other familiar example of the kind. In elevated places where the atmosphere is diffuse, the resistance offered to the passage of solar rays is inconsiderable, but in valleys where the air is condensed through pressure of the mass above, the friction is great, and the resultant heat is intense.

The old theory of solar combustion as a source of heat is untenable for several reasons, the most prominent of which is that the great luminary would have burnt itself out long ago; and another is that as only its planetary bodies and their satellites are recipients of the benefit, stellar space would consume much the larger amount.

In the summer, when the sun is overhead, the impact of solar rays is greater than in winter, when the sun shines slantingly. A sunglass converges solar rays into a focus, and thus multiplies the friction—intensifies the heat at a given spot. The moon has no atmosphere, hence solar rays falling upon it meet with no resistance —evolve no heat.

The suggestion of Proctor that the sun's fires are fed by inflowing meteors as fuel, is also a gratuity. As meteorites become scarce, the heat would decrease—a lack of supplies would have been felt long ago. Besides, in the combustion of so much coarse material what would become of the ashes or debris?

There seems to be but one rational account of the origin of solar heat, and that is through friction. If that be the source of the sun's heating energy, it is to last as long as our atmosphere does, hence may be regarded as abundant and eternal.—HOWE, Matter and Energy.

The Biographies of King, Howe, and Scudder, 1912, was written by Harvey Wickes Felter, M. D.