deeply convinced that when (and I and Sharpe have seen several most
striking and obvious examples) great neighbouring or alternating regions of
true metamorphic schists and clay-slate have their foliations and cleavage
parallel, there is no way of escaping the conclusion, that the layers of
pure quartz, feldspar, mica, chlorite, etc., etc., are due not to original
deposition, but to segregation; and this is I consider the point which I
have established. This is very odd, but I suspect that great metamorphic
areas are generally derived from the metamorphosis of clay-slate, and not
from alternating layers of ordinary sedimentary matter. I think you have
exactly put the chief difficulty in its strongest light--viz. what would be
the result of pure or nearly pure layers of very different mineralogical
composition being metamorphosed? I believe even such might be converted
into an ordinary varying mass of metamorphic schists. I am certain of the
correctness of my account of patches of chlorite schists enclosed in other
schist, and of enormous quartzose veins of segregation being absolutely
continuous and contemporaneous with the folia of quartz, and such, I think,
might be the result of the folia crossing a true stratum of quartz. I
think my description of the wonderful and beautiful laminated volcanic
rocks at Ascension would be worth your looking at. (540/3. "Geological
Observations on S. America," pages 166, 167; also "Geological Observations
on the Volcanic Islands," Chapter III. (Ascension), 1844.)


LETTER 541. TO C. LYELL.
Down, January 14th [1855].

We were yesterday and the day before house-hunting, so I could not answer
your letter. I hope we have succeeded in a house, after infinite trouble,
but am not sure, in York Place, Baker Street.