CHAPTER IV. 



EARTHQUAKES. 



SENSATIONS WHICH THEY PRODUCE. BRIEF ACCOUNTS or I Mi; i:\KTHQUAKES OP 1570, 1647, 1667, 1668, 1722, 1730, 

 1751, 1783, 1819, 1822, 1829, 1835, 1837, 1849. -OUR MODE OF OBSERVING SHOCKS. THE EARTHQUAKE OF DECEMBEE 

 6, 1850; THAT OF APRIL 2, 1851. SUCCEEDING LESSER AGITATIONS, MAY 26, 1851. SEVERAL TREMORS OP ESPECIAL 

 INTEREST. LOCAL AND METEOROLOGICAL INFLUENCES. VOLCANIC THEORY OF EARTHQUAKES. DYNAMICS. 'PERMA- 

 NENT EFFECTS. OTHER ATTRIBUTED RESULTS. CONCLUDING REFLECTIONS. 



Of all terrestrial phenomena in Chile, there is not one so thrilling to the stranger from the 

 temperate zones of the northern hemisphere as that which deprives him of confidence in the 

 immobility of the earth. " From our earliest childhood we are accustomed to contrast the mo- 

 bility of water with the immobility of the earth ; all the evidences of our senses have confirmed 

 this belief ; and when suddenly the ground itself shakes beneath us, a natural force of which we 

 had no previous experience presents itself as a strange and mysterious agency. A single instant 

 annihilates the illusion of our whole previous life ; we feel the imagined repose of nature vanish, 

 and that we are ourselves transported into a realm of unknown destructive forces. Every sound 

 affects us ; our attention is strained to catch even the faintest movement of the air ; we no longer 

 trust the ground beneath our feet."* 



Nor does time ever reconcile him to the recurrence of the convulsions. Every return forces 

 the impression more powerfully on his mind, and with each he recognises his helplessness 

 more painfully. From the lightning and tempest, from the floods of rivers, and, measu- 

 rably, from stormy billows of the ocean, art has enabled him to interpose safeguards ; but the 

 accumulation of that internal agent, the growth of whose pent-up power no mortal eye 

 can watch, no human knowledge neutralize or control, discloses not its hidden laboratories 

 baffles all efforts to foretell its completed volume ; and when least he anticipates it, the elastic 

 crust of the earth, no longer resisting the pressure, is heaving and undulating as the waves of 

 a troubled sea. Sometimes there are no warnings of impending danger, and, in the twinkling 

 of an eye, cities lie level with the plain, their inhabitants buried beneath the ruins ; though, 

 most generally, one of the sound-waves travels more rapidly than the great earth-wave, and 

 there are some few seconds during which one may rush from the danger of crashing walls. 

 With this all knowledge ceases ; the heavy, unmistakable subterranean rumble has bidden yon 

 fly ; the violence or duration of the earth-storm is known only to God. 



Natives of South America have two words by which they designate the phenomenon tern- 

 Hores and terremotos. The former are only partial agitations of the surface, confined to very 

 limited districts, and rarely, or never, producing serious damage; the latter consist of violent 

 upliftings or horizontal oscillations, extending many hundred miles, when the destruction of 

 life and buildings is proportionate to the distance of the localities from the origin of the dis- 

 rupting force. Objects have been so moved during terremotos as to induce the belief that there 

 is sometimes circular or vorticose disturbance of the surface ; but it is by no means certain that 

 such displacements may not be accounted for in another manner. The longer one remains in 

 a region subject to them, the more promptly he follows the custom of the country, and flies at 

 the sound of danger, unfitted, in most instances, for studying either the motions, or other 

 physical facts of interest, during the brief instant allowed him. From the frequency of their 



* KOHOR. Vol. I. 



