written at too great length; and
have amused myself if I have done you no good--so farewell.

LETTER 489. TO C. LYELL. Down, July 5th [1856].

I am very much obliged for your long letter, which has interested me
much; but before coming to the volcanic cosmogony I must say that I
cannot gather your verdict as judge and jury (and not as advocate)
on the continental extensions of late authors (489/1. See "Life and
Letters," II., page 74; Letter to Lyell, June 25th, 1856: also
letters in the sections of the present work devoted to Evolution and
Geographical Distribution.), which I must grapple with, and which as yet
strikes me as quite unphilosophical, inasmuch as such extensions must be
applied to every oceanic island, if to any one, as to Madeira; and this
I cannot admit, seeing that the skeletons, at least, of our continents
are ancient, and seeing the geological nature of the oceanic islands
themselves. Do aid me with your judgment: if I could honestly admit
these great [extensions], they would do me good service.

With respect to active volcanic areas being rising areas, which looks
so pretty on the coral maps, I have formerly felt "uncomfortable" on
exactly the same grounds with you, viz. maritime position of volcanoes;
and still more from the immense thicknesses of Silurian, etc., volcanic
strata, which thicknesses at first impress the mind with the idea of
subsidence. If this could be proved, the theory would be smashed; but
in deep oceans, though the bottom were rising, great thicknesses of
submarine lava might accumulate. But I found, after writing Coral Book,
cases in my notes of submarine vesicular lava-streams in the upper
masses of the Cordillera, formed, as I believe, during subsidence,
which staggered me greatly. With respect to the maritime position of
volcanoes, I have long been coming to the conclusion that there must
be some law causing areas of elevation (consequently of land) and of
subsidence to be parallel (as if balancing each other) and closely
approximate; I think this from the form of continents with a deep ocean
on one side, from coral map, and especially from conversations with you
on immense subsidences of the Carboniferous and [other] periods, and yet
with continued great supply of sediment. If this be so, such areas,
with opposite movements, would probably be separated by sets of parallel
cracks, and would be the seat of volcanoes and tilts, and consequently
volcanoes and mountains would