SCIENCE, INVENTION, DISCOVERY. 



315 



Earthquakes. The phenomena con- 

 nected with earthquakes have been variously 

 described. Many writers refer to appearances 

 in the heavens, or changes in the atmosphere, 

 which to them seem to have some connection 

 with the catastrophes they narrate. They tell 

 of irregularities in the seasons preceding or 

 following the shock ; of sudden gusts of wind, 

 interrupted by sudden calms ; of violent rains 

 at unusual seasons or in countries where such 

 phenomena are almost unknown ; of a redden- 

 ing of the sun's disk ; of a haziness in the 

 air, often continued for months ; and similar 

 phenomena. But these are so irregular in their 

 appearance, and have been so seldom observed 

 associated with more than a single earthquake, 

 that in the absence of any decided reason to 

 the contrary there seems good ground for be- 

 lieving they have no real connection with the 

 earthquake. The general opinion of investi- 

 gators is that these agitations proceed from 

 within outward, and are not of atmospheric or 

 other external origin. True, Professor Alexis 

 Perry, of Dijon, France, thought he discovered 

 relations between the ages of the moon and 

 these occurrences which seemed to sustain the 

 theory of Zantedeschi that the liquid nucleus 

 of the earth responds to the moon's attraction 

 in tides, somewhat as the coast does ; but the 

 theory that the earth has a liquid nucleus cov- 

 ered with only a thin, solid crust is losing ad- 

 herents continually. All theorists are agreed, 

 as to the connection between volcanoes and 

 earthquakes, that they are produced by the 

 same subterraneous agency. Mr. Mallet, in 

 an elaborate report on the subject presented to 

 the British Association, proposed an ingenious 

 theory. He assumes that volcanoes and the 

 centers of earthquake disturbances are near the 

 sea or other large supplies of water ; and he 

 says that when an eruption of igneous matter 

 takes place beneath the sea-bottom the first 

 action must be to open up large fissures in its 

 rocky material, or to lift and remove its inco- 

 herent portions, such as sand, mud, gravel, 

 etc. The water, on meeting the heated sur- 

 face, assumes the spheroidal state. While in 

 this condition the intestine motion may be 

 great, but little steam is generated; but no 

 sooner have the surfaces cooled than the water 

 comes into close contact with them, and a vast 

 volume of steam is evolved explosively and 

 blown off into the deep and cold water of the 

 sea, where it is condensed, and thus a blow 

 of the most tremendous sort is given at the 

 volcanic focus, and, being transferred out- 

 wardly in all directions, is transmitted as the 

 earthquake shock. Whatever their origin, 

 whether of one cause or various causes, the 

 prevailing opinion still is that the vibrations of 



every earthquake can be traced to a focus 

 within the earth, and that this lies directly be- 

 neath the point of greatest disturbance ou the 

 earth's surface. There are creditable records 

 of between 6,000 and 7,000 earthquakes, be- 

 tween 1606 B. C. and A. D. 1842. In the 

 great Lisbon earthquake no less than 60,000 

 perished, while in that of Calabria, in the end 

 of the last century, 40,000 were destroyed. It 

 is estimated that at least 13,000,000 of the 

 human race have perished in this way. 



Electric Light, The, wat first invented 

 by Sir Humphry Davy, in. the early part of 

 this century, who produced the arc light with 

 a battery of 2,000 cells. It was not in prac- 

 tical use, however, until 1844, when improve- 

 ments in its manner of construction were 

 made by a Frenchman named Foucault, and 

 it was used to illuminate the Place de la Con- 

 cord, in Paris. In 1855, Jules Duboscq's 

 electric lamp thus far the most perfect of 

 the kind was shown at the Paris Exposi- 

 tion ; but, though improvements were made 

 in the invention during the twenty years fol- 

 lowing, little was accomplished toward practi- 

 cal electric lighting until the invention of 

 Jablochkoff's candle. Paul Jablochkoff was 

 a Russian, who resigned his position under 

 the government in 1875 to devote his time 

 wholly to scientific study. It was his inten- 

 tion to visit the Centennial Exposition in Amer- 

 ica, but he was induced to remain in Paris, 

 where, in 1876, he produced the electric can- 

 dle, whose discovery made a great sensation. 

 The light given by this candle was soft 

 and steady, and a great many of them speedily 

 came into use in Europe. In the last fifteen 

 years great progress has been made, and there 

 are now many different styles and forms, but 

 in their essential features they nearly all come 

 under two general classes the arc light and 

 the incandescent light. The arc light is, in 

 principle, the same as that invented by Davy, 

 the improvements consisting in different de- 

 vices for regulating and maintaining at a 

 constant distance the tips, and in different 

 preparations for the substance of these tips, 

 which are generally of carbon. The light is 

 produced as follows : Two tips connected with 

 the opposite poles of a strong battery are 

 brought near to each other. The electricity, 

 overcoming the resistance of the air, jumps 

 from one tip to the other, and in so doing gen- 

 erates such an intense heat that the particles 

 on the end of the one tip are volatilized and 



1 carried to the other in a condition of white heat, 

 forming an arc of light of intense brilliancy. 



! Thus one tip is slowly consumed and the other 

 somewhat increased, and hence the necessity 

 of regulators for the tips, whence these lights 



