CONCEPCION. 59 



rendinj^ and injection would, if repeated often 

 enough (and we know that earthquakes repeatedly 

 aflect the same areas in the same manner), form a 

 chain of hills ; and the linear island of St. Mary, 

 which was upraised thrice the height of the neigh- 

 bouring country, seems to be undergoing this pro- 

 cess. I believe that the solid axis of a mountain 

 differs in its manner of fonnation from a volcanic 

 hill only in the molten stone having been repeat- 

 edly injected instead of having been repeatedly 

 ejected. Moreover, I believe that it is impossible 

 to explain the structure of great mountain-chains, 

 such as that of the Cordillera, where the strata, 

 capping the injected axis of Plutonic rock, have 

 been thrown on their edges along several parallel 

 and neighbouring lines of elevation, except on this 

 view of the rock of the axis having been repeatedly 

 injected, after intervals sufficiently long to allow 

 the upper parts or wedges to cool and become 

 solid ; for if the strata had been thrown into their 

 present highly-inclined, vertical, and even inverted 

 positions by a single blow, the very bowels of the 

 earth would have gushed out ; and instead of be- 

 holding abrupt mountain-axes of rock solidified 

 under great pressure, deluges of lava would have 

 flowed out at innumerable points on every line of 

 elevation.* 



* For a full account of the volcanic phenomena which accom- 

 panied the earthquake of the 20th, and for the conclusions dedu- 

 cible from them, I must refer to volume v. of the Geological 

 Transactions. 



