26o THE POPULAR SCIENCE MONTHLY. 



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 mystify- 

 ing 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 im- 

 portance 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. — Long- 

 man's Magazine. 



It 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 cham- 

 pioned 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. 



