PROCEEDmOS OF THE PoLTTECHKIC ASSOCIATION. 787 



There are hundreds of the like instances on record, and no doubt. 



when we come to get full scientific accounts of the late convulsion, it 

 will be found that parts of the coast of South America have been 

 raised above their former level. 



Such is the way in which earthquakes do their work, and they are 

 alioays at work. According to Humboldt, there is not a day in which 

 the earth is not shaken by these commotions ; so that the state of per- 

 petual movement is the normal condition of the surface of our globe, 

 and, if we had apparatus sufficiently sensitive, we should doubtless 

 detect this constant movement. And, indeed, already astronomers 

 complain that their instruments betray, by inexplicable perturbations, 

 the instability of the crust that supports them. 



It is true that over by far the larger part of the globe these agitations 

 are either slight, or else absolutely imperceptible, so that we consider 

 the greater portion of the earth as motionless ; but there are other 

 countries that have again and again been rudely shaken by violent 

 and destructive convulsions. These are tlie true regions of the earth- 

 quake and volcano, and modern physical geography has made such 

 progress as to mark off a certain number of extensive districts or zones 

 in which the shocks are simultaneous. Among these may be men- 

 tioned the Atlantic district, that of Central Asia, and that of the 

 Pacific ocean. 



Of these great regions, the zone embracing the Andes of South 

 America is one of the best defined, and it is that divulsed by the 

 late earthquake waves. It extends from the southward of Chili to 

 the northward of Quito, from about latitude forty three degrees south, 

 to about two degrees north of the equator. In this region, compre- 

 hending forty-five degrees of latitude, or above 3,000 miles, there is a 

 great chain of volcanic cones, arranged in a linear direction. In 

 Quito, Peru and Chili there are twenty-six of these in activity, and 

 nearly as many more extinct ones, any one of which, as geologists 

 tell us, may at any moment break out afresh. In this whole region 

 earthquakes of more or less violence are of very frequent occurrence. 

 Boussingault declares his belief that if a full register had been kept 

 of all the convulsions experienced in this zone, it would be found that 

 the trembling of the earth had been incessant. Xor is the frequency 

 of these South American earthquakes more extraordinary than the 

 duration of the shocks. Humboldt relates that on one occasion, 

 when traveling on mule back with his companion Bonpland, they 

 were obliged to dismount in a dense forest and throw themselves on 



