630 C. Darwin, Esq., on Volcanic 



the grandeur of the one motive power, which, causing the elevation of the 

 continent, has produced, as secondary effects, mountain-chains and vol- 

 canos. The same reasons which led me to the conviction, that the train of 

 connected volcanos in Chile and the recently uplifted coast, together more 

 than 800 geographical miles in length, rested on a sheet of fluid matter, are ap- 

 plicable with nearly equal force to the areas beneath the other trains. We see 

 that these areas are connected by one uniform chain of mountains, from many 

 distant points of which fluid rock is yearly ejected; and as there are proofs 

 that nearly the whole west coast of South America has been elevated within 

 a period geologically modern, and that this movement, in some parts at least, 

 has extended across the continent, — keeping, also, in mind the probability, 

 that during periods of increased subterranean action, such as those indicated 

 in the foregoing tables, the whole western part of the continent has been al- 

 most simultaneously affected, it appears to me, that there is little hazard in 

 assuming, that this large portion of the earth's crust floats in a like manner 

 on a sea of molten rock. Moreover, — when we think of the increasing tem- 

 perature of the strata, as we penetrate downwards in all parts of the world, and 

 of the certainty that every portion of the surface rests on rocks which have once 

 been liquefied ; — when we consider the multitude of points from which fluid 

 rock is annually emitted, and the still greater number of points from which it 

 has been emitted during the few last geological periods inclusive, which, as 

 far as regards the cooling of the rock in the lowest abysses, may probably be 

 considered as one, from the extreme slowness with which heat can escape 

 from such depths ; — when we reflect how many and wide areas in all parts 

 of the world are certainly known, some to have been rising and others sink- 

 ing during the recent aera, even to the present day, and do not forget the in- 

 timate connexion which has been shown to exist between these movements 

 and the propulsion of liquified rock to the surface in the volcano; — we are 

 urged to include the entire globe in the foregoing hypothesis. 



To the belief in these large seas of molten rock, not to speak of an entire 

 concentric layer so constituted, it has been objected, that if its fluidity be to- 

 lerably perfect, (which there is good reason to think is the case from what we 

 see of the junction of the plutonic with the metamorphic formations,) the lava 

 ought to stand (supposing a comparative examination possible) at nearly equal 

 heights, within neighbouring volcanic orifices. To this I may answer, if it be 

 permitted me to assume that the subsiding as well as the rising areas rest on a 

 fluid surface, that whatever the power is which causes one to rise and another 

 to sink, acts with unequal force (greatly modified, also, by unequal resistance) 

 in different parts of even a very limited area. The main strength of the earth- 



