Phenomena in South America. 629 



must have been pumped into the axis by as many separate strokes ; nor did the 

 process cease for many subsequent months*. In the central ridges of the Cor- 

 dillera^ there are masses of compact unstratified rocks, half again as lofty as 

 Etna, and I believe, from the reasoning above given, that they were formed 

 by steps nearly as slow as those indicated by the innumerable layers of volcanic 

 matter accumulated on the flanks of the Sicilian mountain. In the volcano, 

 that is, a mountain which has been ruptured in its incipient state, the fluid 

 stone being brought to the surface is rapidly cooled, and hence successive 

 layers are formed ; but in the axis of plutonic formation (or subterranean 

 volcano, if it may be so called), the injected matter, not being rapidly cooled, 

 is blended into one huge conical pile. This whole view is nothing more than 

 an application of Hutton's doctrine of the repetition of small causes to produce 

 great effects ; and which Mr. Lyell has already brought distinctly to bear on 

 this particular subject. 



The action of the elevatory force, as known by beds of littoral shells, suc- 

 cessive lines of aqueous erosion on cliffs of solid rock, and terraces rising one 

 above another, seems everywhere to have been prolonged, although inter- 

 mittently : in the volcano, the structure of the mountain, as well as all history, 

 bespeaks the same fact with respect to the eruptive force. During the Con- 

 cepcion earthquake, we have seen that these powers, so analogous in their ac- 

 tion, were absolutely parts of one common phenomenon. Bearing in mind 

 Mr. Hopkins's demonstration, if there be considerable elevation, there must be 

 fissures, and, if fissures, almost certainly unequal upheaval, or subsequent 

 sinking down, — the argument may be finally thus put : — mountain-chains are 

 the eff*ects of continental elevations ; continental elevations and the eruptive 

 force of volcanos are due to one great motive power, now in progressive 

 action ; therefore the formation of mountain-chains is likewise in progress, 

 and at a rate which may be judged of by either phenomenon, but most nearly 

 by the growth of volcanos. 



Concluding Remarks. 

 With these views, if we look at a map of America, and observe the con- 

 tinuity of the great chain of the Andes, and its lesser parallel ones, in which 

 from lat. 55° 40' South to 60" North, a space of little less than 7000 miles, 

 the volcanic forces either now are, or recently have been, in action, — and 

 likewise the symmetry of the whole, — we shall be deeply impressed with 



* In an extract from a letter, dated Concepcion, May 6th, that is seventy-six days after the 

 great earthquake, there is this passage : — " It is only since a few days, that a day has passed 

 witliout a shock, and even yesterday we had one." 



4m2 



