SCIENCE AND TRAVEL 203 



forces are Darwin received demonstration on the 

 coast of Chile in 1835. Under date of February 12, 

 he writes : " This day has been memorable in the 

 annals of Valdivia for the most severe earthquake 

 experienced by the oldest inhabitant. ... A bad 

 earthquake destroys our oldest associations ; the 

 earth, the very emblem of solidity, has moved be- 

 neath our feet like a thin crust over a fluid." He 

 observed that the most remarkable effect of this 

 earthquake was the permanent elevation of the land. 

 Around the Bay of Concepcion it was raised two or 

 three feet, while at the island of Santa Maria the 

 elevation was much greater ; " on one part Captain 

 Fitzroy found beds of putrid mussel shells still 

 adhering to the rocks, ten feet above high-water 

 mark." On the same day the volcanoes of South 

 America were active. The area from under which 

 volcanic matter was actually erupted was 720 miles 

 in one line and 400 in another at right angles to it. 

 Great as is the force at work, ages are required to 

 produce a range of mountains like the Cordilleras; 

 moreover, progress is not uniform and subsidence 

 may alternate with elevation. It was on the princi- 

 ple of the gradual subsidence (and elevation) of the 

 bed of the Pacific Ocean that Darwin accounted for 

 the formation of coral reefs. Nothing "is so unsta- 

 ble as the level of the crust of this earth." 



Closely associated with the evidence of the im- 

 mensity of the force of volcanic action and the in- 

 finitude of time elapsed, Darwin had testimony of 

 the multitude of plant and animal species, some gi- 

 gantic, others almost infinitely small, some living, 

 others extinct. We know that his thought was greatly 



