512 CONCEPCION. [cHaP. xIv. 
necessarily consequent on the tension of the land when upraised, 
and their injection by fluidified rock. This rending and injec- 
tion would, if repeated often enough (and we know that earth- 
quakes repeatedly affect 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 neighbouring country, seems to 
be undergoing this process. I believe that the solid axis of a 
mountain, differs in its manner of formation from a volcanic hill, 
only in.the molten stone having been repeatedly 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 in- 
jected 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 in- 
jected, 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 in- 
verted positions, by a single blow, the very bowels of the earth 
would have gushed out; and instead of beholding 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 accompanied the 
earthquake of the 20th, and for the conclusions deducible from them, I must 
refer to Volume V, of the Geological Transactions. 
