EARTHQUAKES. 161 



number of earthquakes than we in Europe of that of the 

 showers of rain, and where Bonpland and I were compelled 

 to dismount, from the rcstivencss of our mules, because the 

 earth shook in a forest for 15 to 18 minutes without intermis- 

 sion. By such long custom, as Boussingault subsequently 

 experienced even in a still higher degree, one becomes fitted 

 for quiet and careful observation, and also for collecting 

 varying evidence with critical care on the spot, nay, even 

 for examining under what conditions the mighty changes of 

 the surface of the earth, the fresh traces of which one recog- 

 nizes, have taken place. Although five years had already 

 elapsed since the terrible earthquake of Riobamba, which, 

 on the 4th of February, 1797, destroyed upward of 30,000 

 people in a few minutes,* we nevertheless saw the formerly- 

 advancing cone of the Moya f which rose out of the earth, 

 and witnessed the employment of this combustible substance 

 for cooking in the huts of the Indians. I might describe the 

 results of alterations of the ground from this catastrophe, 

 which, although on a larger scale, were exactly analogous to 

 those presented by the famous earthquake of Calabria (Feb- 

 ruary, 1783), and were long considered to have been repre- 

 sented in an incorrect and exaggerated manner, because they 

 could not be explained in accordance with hastily-formed 

 theories. 



By carefully separating, as we have already indicated, 

 the investigation of that which gives the impulse to the vi- 

 bration, from that of the nature and propagation of the 

 waves of commotion, we distinguish two classes of problems 

 of very unequal accessibility. The former, in the present 

 state of our knowledge, can lead to no generally satisfactory 

 results, as is the case with so many problems in which we 

 wish to ascend to primary causes. Nevertheless, while we 

 are endeavoring to discover laws in that which is submitted 

 to actual observation, it is of great cosmical interest that we 

 should bear constantly in mind the various genetic explana- 

 tions which have hitherto been put forward as probable. 

 As with all vulcanicity, the greater part of these refer, 

 under various modifications, to the high temperature and 

 chemical nature of the fused interior of the earth ; one of 



* I follow the statistical account communicated to me by the Cor- 

 regidor of Tacunga in 1802. It rose to a loss of 30,000—34,000 peo- 

 ple, but some twenty years later the number of those killed immedi- 

 ately was reduced by about one third. 



t Cosmos, vol. i., p. 213. 



