Page:Popular Science Monthly Volume 7.djvu/647

Rh of his theory in the drowsiness which settles down on elderly men over their wine. "Nature says to them, 'Go to bed.' They will not go to bed, but still Nature will not allow her law to be broken, so she sends them to sleep sitting in their chairs." But, then, does not Nature quite as clearly indicate, by means of the nightmares and the unrest with which she torments the would-be sleeper who has gone to bed directly after a heavy meal, that a full stomach is not the best preparation for slumber? Many persons with whom this prescription for sleep would fail, may perhaps find another prescription given by Mr. Buckland more effectual, viz., eating onions, the essential oil of which possesses highly-soporific powers.

The Use of Paris-Green.—The use of Paris-green in dealing with the Colorado beetle has been condemned on the ground both that it poisons the soil, rendering it sterile, and that it is liable to be absorbed by the plant. Certain experiments made by Mr. McMurtrie, chemist of the Department of Agriculture, throw much light upon this question, and therefore are worthy of reproduction here. To determine the first point, that is, whether the Paris-green poisons the soil, Mr. McMurtrie planted peas in a number of flower-pots, each containing the same amount of earth, and all but one containing a certain proportion of Paris-green. The proportion of this substance varied from 100 milligrammes up to five grammes. The first five pots contained Paris-green as follows: No. 1, none; No. 2, 100 milligr.; No. 3, 200; No. 4, 300; No. 5, 400. In all of these the peas grew equally. In No. 6, containing 500 milligrammes, the plant was less vigorous than in No. 5. This, then, may be regarded as the proportion of Paris-green which impairs the fertility of soil. As the proportion increases, the plant grows feebler and feebler till No. 12 is reached, containing two grammes of Paris-green. Here the plant barely appears above the surface. In the rest of the pots, containing respectively three, four, and five grammes, the plant sends no shoot above the surface.

The proportion of 500 milligrammes in the flower-pot No. 6 is equal to 145.6 grammes per cubic foot, or 906.4 pounds per acre, I calculating for a depth of one foot. Now, as less than two lbs. of Paris-green per acre is enough to use in warring against the beetle, it would take about 500 years to poison the soil, supposing the green to be applied every year, and that it was all retained. "But when rotation of crops is practised," says Mr. McMurtrie, "and application of the poison cannot therefore take place upon the same plot more than once in three or four years, it is probable that each application, being acted on by the natural solvents of the soil, will be removed by drainage before another is made." To the question whether arsenic can be absorbed and assimilated by the plant in the economy of growth, he replies in the negative. All of the plants grown, from the largest to the smallest, were examined according to Marsh's test for arsenic, but its presence could not be detected.

Periodicity of Thunder-storms.—W. von Bezold lately presented to the Munich Academy of Science a paper on the "Periodicity of Thunder-storms," basing his remarks upon a series of observations which extended over a period of 105 years prior to 1869. A synopsis of this paper we here reproduce from the American Journal of Science. He finds that in years when the temperature is high and the sun's surface relatively free from spots, thunder-storms are abundant. But as the maxima of the sun-spots coincide with the greatest intensity of auroral displays, it follows that both groups of phenomena, thunder-storms and auroras, to a certain extent supplement each other, so that years of frequent storms correspond to these auroras, and vice versa. He observes that such a connection between sun-spots and storms does not by any means sanction the supposition of a direct electrical interaction between the earth and the sun, but may be simply a consequence of a degree of insolation dependent upon the sun-spots.

These changes in the insolation, according to Köppen, manifest themselves in different latitudes not contemporaneously but successively. The phenomena of thunderstorms, on the other hand, do not depend alone upon the condition of the place in question with respect to temperature, but also on the condition of the atmosphere at