5H THE POPULAR SCIENCE MONTHLY. 



ests waved like standing corn in a gale of wind, and an area 70 miles 

 long by 30 miles wide was submerged, and became a swampy lake. 



On the 13th of August, 1868, a fearful earthquake took place in 

 Peru, which laid waste much of the country lying between the Andes 

 and the Pacific. The shocks were felt through a distance of 1,400 

 miles north and south, and three important cities were destroyed. At 

 Arequipa, in Peru, 40 miles from the sea, a slight undulatory shock 

 was felt, followed by others so violent that in five minutes not a house 

 was standing in that city of 44,000 inhabitants. A subterranean 

 rumbling, like the rush of an avalanche, was heard above the crash, 

 and a cloud of dust rose in the still air over the city. On the sea- 

 coast were situated Iquique and Arica both were destroyed by the 

 shocks, and overwhelmed by a tremendous wave. The ocean thus 

 took up the vibrations of the land, and waves of tremendous volume 

 were put in motion, which rolled, not only upon the coast, but away 

 from it with a velocity in the deep ocean of not less than 400 miles an 

 hour. The great wave for one was of much greater volume than 

 the others has been estimated at upward of 200 miles breadth, with 

 a length along its curved crest of 8,000 miles. This rolled into the har- 

 bor of Yokohama, in Japan, 10,500 miles distant, and was felt at Port 

 Fairy, in South Victoria, distant nearly one-half of the earth's cir- 

 cumference. 



In 1797, a province of Ecuador, about 100 miles south of Quito, 

 was visited by what is described by Humboldt as " one of the most 

 fearful phenomena recorded in the physical history of our planet." 

 The shocks were vertical, and occurred as " mine-like explosions." 

 The town of Riobamba was over the central area, and many of its 

 inhabitants were thrown 100 feet into the air. 



The shocks, in this instance, were not announced by any subter- 

 ranean thunder, but, just 18 minues after, a terrific roar was heard be- 

 neath Quito. It thus appears that shocks are not always preceded by 

 sounds, nor do the sounds increase with the violence of the shock. 



Sometimes, says Humboldt, there is a " ringing noise, as if vitrified 

 masses were struck ; again, a continuous rumbling and hollow roar ; 

 at others, a rattling and clanking as of chains or near thunder." With 

 the lightning's flash we know that the danger is over, and await the 

 coming thunder without alarm ; but thunder, rolling deep in the earth, 

 announces possible if not certain calamity. 



Throughout the region of the Andes a connection between volcanic 

 and earthquake action has been recognized by the people. It was 

 supposed by Strabo that volcanoes are safety-valves, and scientific 

 observation suggests that they may relieve the pressure and tension 

 which would otherwise lay the earth in ruins. 



For two years previous to 1538 earthquakes had been violent and 

 frequent at Pozzuoli on the Bay of Baise, and elsewhere in the vicinity 

 of Naples. On the 27th and 28th of September they did not cease day 



