Page:Popular Science Monthly Volume 40.djvu/272

260 evils of a pestilence. At the same time it should be known that smoke-particles can be deposited by the agency of electricity. If an electric discharge be passed through a jar containing smoke, the dust will be deposited so as to make the air clear. Lightning clears the air, restoring the devitalized oxygen and depositing the dust on the ground. Might it not, then, be possible for strong enough electrical discharges from several large voltaic batteries to attack the smoke in the air of large cities, and especially the fumes from chemical works, so as to bring down the dust In the form of rain instead of leaving it in the form of mystifying fog?

Organic germs also float in the air. Some are being vomited into the air from the pestilential hot-beds of the lowest slums. In a filthy town no less than thirty millions of bacteria in a year will be deposited by the rain upon every square yard of surface. A man breathes thirty-six germs every minute in a close town, and double that in a close bedroom. The wonder is how people escape sickness, though most of these germs are not deadly. In a healthy man, however, the warm lung surfaces repel the colder dust-particles of all kinds, and the moisture evaporating from the surface of the air-tubes helps the prevention of the dust clinging to the surface.

From this outline the reader will observe the increasing importance of careful attention to the influence of dust in the economy of nature. As a sickness-bearer and a death-bearer it must be attacked and rendered harmless; as a source of beauty unrivaled we must rejoice at its existence. The clouds that shelter us from the sun's scorching heat, the refreshing showers that clear the air and cheer the soil, the brilliancy of the deep blue sea and lake, the charms of twilight, and above all the glory of the colors of sunrise and sunset, are all dependent upon the existence of millions of dust-particles which are within the power of man's enumeration. No more brilliant achievement has been made in the field of meteorology than during the past few years by the careful observation and inventive genius of Mr. Aitken in connection with the importance of dust in air and water.—Longman's Magazine.

appears, from the complete edition of the works of Huygens, now in course of publication at The Hague, that as soon as he had succeeded in applying the pendulum to the regulating of clocks, claims were set up for priority in the invention. The best-founded claims were those of Galileo, which were championed by Prince Leopold de' Medici. According to the formal statement drawn up by Viviani, Galileo had conceived the idea, but failed to make the application of it. He had a pendulum connected with wheel-work, but omitted to provide any weights, springs, or other means of keeping the machinery in motion.