arthquake 



SCIENTIFIC SIDE-LIGHTS 



192 



unique interest. She in all probability 

 shared the origin of the earth ; she perhaps 

 prefigures its decay. She is at present its 

 minister and companion. Her existence, so 

 far as we can see, serves no other purpose 

 than to illuminate the darkness of terres- 

 trial nights, and to measure, by swiftly re- 

 curring and conspicuous changes of aspect, 

 the long span of terrestrial time. Inquiries 

 stimulated by visible dependence, and aided 

 by relatively close vicinity, have resulted in 

 a wonderfully minute acquaintance with the 

 features of the single lunar hemisphere open 

 to our inspection. CLEBKE History of As- 

 tronomy, pt. ii, ch. 7, p. 322. (Bl., 1893.) 



944. EARTH'S GIRDLE Electric Tele- 

 graph Submarine Lines of Telegraph. 

 About the middle of the last century it was 

 perceived by a few students of electricity 

 that it afforded a means of communication 

 at a distance; but it was not till the year 

 1837 that the efforts of many simultaneous 

 workers overcame the numerous practical 

 difficulties, and the first electric telegraph 

 was established. Its utility was so great, 

 especially in the working of the railways 

 then being rapidly extended over the king- 

 dom, that it soon came into general use. 

 The first submarine line was laid from 

 Dover to Calais in 1851 ; and only five years 

 afterward, in 1856, a company was formed 

 to lay an electric cable across the Atlantic. 

 The cable, 2,500 miles long and weighing a 

 ton per mile, was successfully laid, in 1858, 

 from Ireland to Newfoundland; but owing 

 to the weakness of the electric current, and 

 perhaps to imperfections in the cable, it soon 

 became useless, and had to be abandoned. 

 After eight years more of invention and ex- 

 periment, another cable was successfully 

 laid in 1866; and there are now no less 

 than fourteen lines across the Atlantic, 

 while all the other oceans have been elec- 

 trically bridged, so that messages can be 

 sent to almost any part of the globe at a 

 speed which far surpasses the imaginary 

 power of Shakespeare's sprite Ariel, who 

 boasted that he could " put a ' girdle round 

 about' the earth in forty minutes." WAL- 

 LACE The Wonderful Century, ch. 3, p. 21. 

 (D. M. & Co., 1899.) 



945. EARTH'S RETURNING FRAG- 

 MENTS Meteorites Perhaps of Earthly Origin. 

 Well, these stones from the sky being of 

 the same composition as the minerals of 

 which our own planet is formed, is it not 

 natural to ask simply whether they may not 

 have had the earth itself for their origin? 

 But how ? May not the violent volcanoes of 

 geological times, the eruptions, the tremen- 

 dous conflagrations, the fierce fires of the 

 ancient pandemonium, have shot into space 

 lava, scoria, stones, with such a force of 

 projection that these objects would be des- 

 patched to thousands, millions, hundreds of 

 millions of miles, in orbits which would not 

 take less than a thousand, ten thousand, a 

 hundred thousand years or more to describe ? 



If our planet has been able to give birth to 

 such projectiles, it does not form an excep- 

 tion in the universe, and the other celestial 

 bodies may be in the same case. Thus, the 

 sun itself is seen to be almost constantly 

 surrounded with tremendous metallic gase- 

 ous eruptions, which are shot out to thou- 

 sands and even hundreds of thousands of 

 miles above its surface. This is the most 

 rational hypothesis. Such eruptions may 

 take place on all worlds. However, the ter- 

 restrial eruptions would make the products 

 return to us, whereas the others would be 

 sent in all directions. Moreover, the iden- 

 tity of structure of most of the uranoliths 

 with terrestrial minerals presents itself as 

 an eloquent witness in favor of this hypoth- 

 esis, which may be summed up thus : 



Most of the stones which fall from the sky 

 may be natives of the earth itself, having 

 been projected into space by the volcanic 

 eruptions of geological times. FLAMMARION 

 Popular Astronomy, bk. v, ch. 4, p. 549. 

 (A.) 



946. EARTH'S SWIFT REVOLUTION 



The Sun's Ceaseless Control. If the earth 

 could be suddenly stopped in her orbit, and 

 allowed to fall unobstructed toward the sun 

 under the accelerating influence of his at- 

 traction, she would reach the center in about 

 two months. I have said if she could be 

 stopped, but such is the compass of her orbit 

 that, to make its circuit in a year, she has 

 to move nearly 19 miles a second, or more 

 than fifty times faster than the swiftest 

 rifle-ball; and in moving 20 miles her path 

 deviates from perfect straightness by less 

 than one-eighth of an inch. And yet, over 

 all the circumference of this tremendous 

 orbit, the sun exercises his dominion, and 

 every pulsation of his surface receives its 

 response from the subject earth. YOUNG 

 The Sun, ch. 1, p. 37. (A., 1898.) 



947. EARTH-CRUST AFLOAT ON A 

 PLASTIC OCEAN The Solid Center Has 

 Different Revolution. Nevertheless, inas- 

 much as solidification would occur at the 

 surface, where the radiation of heat would 

 take place most rapidly, and as the descend- 

 ing solid matter would be gradually lique- 

 fied, it seems certain that for a long time 

 the solid portions of the earth, tho not form- 

 ing a solid crust, would occupy the exterior 

 parts of the earth's globe. After a time, 

 the whole globe would have so far cooled 

 that a process of aggregation of solid matter 

 around the center of the earth would take 

 place. The matter so aggregated consisted 

 probably of metallic and metalloidal com- 

 pounds denser than the material forming 

 the crust of the earth. Between the solid 

 center and the solidifying crust there would 

 be a shell of unconcealed matter, gradually 

 diminishing in amount, but a portion prob- 

 ably retaining its liquid condition even to 

 the present time, whether existing in iso- 

 lated reservoirs, or whether, as Scrope 

 opines, it forms still a continuous sheet sur- 



