Your letter was forwarded me here. I was the more glad to receive it, as I
never dreamed of your being able to find time to write, now that you must
be so very busy; and I had nothing to tell you about myself, else I should
have written. I am pleased to hear how extensive and successful a trip you
appear to have made. You must have worked hard, and got your Silurian
subject well in your head, to have profited by so short an excursion. How
I should have enjoyed to have followed you about the coral-limestone. I
once was close to Wenlock (532/1. The Wenlock limestone (Silurian)
contains an abundance of corals. "The rock seems indeed to have been
formed in part by massive sheets and bunches of coral" (Geikie, "Text-book
of Geology," 1882, page 678.), something such as you describe, and made a
rough drawing, I remember, of the masses of coral. But the degree in which
the whole mass was regularly stratified, and the quantity of mud, made me
think that the reefs could never have been like those in the Pacific, but
that they most resembled those on the east coast of Africa, which seem
(from charts and descriptions) to confine extensive flats and mangrove
swamps with mud, or like some imperfect ones about the West India Islands,
within the reefs of which there are large swamps. All the reefs I have
myself seen could be associated only with nearly pure calcareous rocks. I
have received a description of a reef lying some way off the coast near
Belize (terra firma), where a thick bed of mud seems to have invaded and
covered a coral reef, leaving but very few islets yet free from it. But I
can give you no precise information without my notes (even if then) on
these heads...

Bermuda differs much from any other island I am acquainted with. At first
sight of a chart it resembles an atoll; but it differs from this structure
essentially in the gently shelving bottom of the sea all round to some
distance; in the absence of the defined circular reefs, and, as a
consequence, of the defined central pool or lagoon; and lastly, in the