Page:Popular Science Monthly Volume 30.djvu/298

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following results: 1. That the oil- and gas-lights, when shown through similar lenses were equally affected by atmospheric variation; 2. That the electric light is absorbed more largely by haze and fog than either the oil- or the gas-light; and, 3. That all three are nearly equally affected by rain. The final conclusions of the committee are that for ordinary necessities of lighthouse illumination mineral oil is the most simple and economical illuminant; aud that for salient headlands, important land-falls, and places where a very powerful light is required, electricity oHers the greatest advantages.

Heredity and Education.—"Heredity and Education; their Relation to Each Other aud to the Human Race," is the title of an address by Dr. E. A. Wood, as President of the Pennsylvania Medical Society. The author holds very positive views on the subject, both as to the excellence to which he would have us aim to bring the race, and with regard to the means to be used to reach the end. "If such a man as Shakespeare," he asks, "has lived, why may not men as great as he live again; and if one man attained this greatness, why may not the average man? If the old Greeks reached such perfect development, why may not Americans? Is it possible that we have reached the zenith of our possibilities? Is it not rather probable that Shakespeare approximated but did not attain the possible average of human development? . . . Nature has written all over her page that Newton and Shakespeare were not accidents, but advance heralds, proclaiming the coming man. No man can conceive of the latent potentiality of the human race; by right effort continued in the right direction, man may be developed into a being grander than I his loftiest ideals." Further: "Let it be written that many races of men have improved, are improving, and bid fair still further to improve; but man has not improved in accord with his powers and opportunities, has not reached the standard of excellence reached two thousand years ago, and is not improving so rapidly as are the animals domesticated by him. The first step toward race improvement must be to teach our children that reproduction is the highest and noblest function of the animal. We are losing time by not teaching this lesson, and all implied by it, immediately and thoroughly."

The Future of the Supply of Plant-Food.—Vice-President Wiley began his address before the Chemical Section of the American Association—which was on "The Economical Aspect of Agricultural Chemistry"—with a rough estimate of the money value of the potash, phosphoric acid, and nitrogen contained in a single harvest, the total of which he placed at $3,343,786,050. This seems to be an enormous quantity of plant-food to be removed from the soil annually, but it must be remembered that it is not all lost; much of it is left in the soil in roots, straw, stalks, etc. But too often the débris is got rid of as quickly as possible, and we have in practice not tilling but killing the soil. The stores of plant-food which have accumulated in our virgin soils are indeed great, but they can not withstand this constant drain upon them. The potash that is in the soil may be estimated as enough to last two hundred and fifty years, and the phosphoric acid two hundred and twenty-five years. Immense reserves of both substances are, however, existent and accessible—the potash in feldspathic rocks, and phosphorus in the phosphate-beds. Still, the exportation of agricultural products becomes a slow but certain method of securing soil exhaustion. In point of fact, however. Professor Wiley further showed, the impoverishment of the soil takes place at a much slower rate than the theory announced above would indicate. Doubtless, much reserve food is brought from the subsoil, and, if it be possible for the subterranean stores of these materials to gradually work their way surface-ward, even the remote future need not fear a dearth of them. There is also a certain conservatism in crops, a vegetable "good breeding," which prevents the growing plant from taking all the food in sight. As long as there is abundance, the plant is a hearty eater; but, when the visible quantity of food falls to a certain minimum, it remains for a long time without any rapid diminution. Respecting the nitrogenous food of plants. Professor Wiley presented a series of studies from