346 



ruary, 1835, but who assured me that he was not aware of 

 there having been any earthquake until his arrival at Mendoza, 

 where it had been felt, and he then heard of it. Nevertheless 

 this earthquake was one of the most violent upon record. 

 Mr. Darwin, who was with the Beagle on the coast of Con- 

 cepcion at that time, says, " the effect of the vibration on the 

 hard primary slate which composes the foundation of the 

 island (of Quiriquina, Concepcion Bay) was still more 

 curious : the superficial parts of some narrow ridges were 

 as completely shivered as if they had been blasted by gun- 

 powder." 



The above-mentioned circumstances, together with having 

 myself personally experienced several severe earthquakes, 

 naturally attracted my attention to the subject, and I have 

 for some years been in the habit of reading whatever related 

 thereunto, whether in works on Geology or in newspapers ; 

 and two years since, while preparing two papers for the 

 Sheffield Literary and Philosophical Society, I carefully 

 examined every book to which I could obtain access on 

 earthquakes and volcanoes, but, with the exception of Baron 

 Humboldt, I was not able to discover that any Geologist had 

 noticed the singular fact of earthquakes having been felt at 

 considerable distances, while portions of intermediate ground 

 remained unaffected. That illustrious traveller mentions the 

 above fact in his Personal Narrative; and in his Cosmos 

 (Translation 28th June, 1845, by J. P. T., pages 221 and 

 222) are the following expressions: — Could we have daily 

 news of the state of the whole of the earth's surface, we 

 should, in all probability, become convinced that some point 

 or other of this surface is ceaselessly shaken ; that there is 

 uninterrupted reaction of the interior upon the exterior going 

 on." * * " It is not the chemical nature of the constituents, 

 but the mechanical structure of the mineral species, that 

 modifies the propagation of the motion, the wave of succus- 



