. On the whole, I lean
to the side that the continents have since Cambrian times occupied
approximately their present positions. But, as I have said, the question
seems a difficult one, and the more it is discussed the better.

LETTER 498. TO A. AGASSIZ. Down, January 1st, 1881.

I must write a line or two to thank you much for having written to me so
long a letter on coral reefs at a time when you must have been so busy.
Is it not difficult to avoid believing that the wonderful elevation
in the West Indies must have been accompanied by much subsidence,
notwithstanding the state of Florida? (498/1. The Florida reefs cannot
be explained by subsidence. Alexander Agassiz, who has described these
reefs in detail ("Three Cruises of the U.S. Coast and Geodetic Survey
Steamer 'Blake,'" 2 volumes, London, 1888), shows that the southern
extremity of the peninsula "is of comparatively recent growth,
consisting of concentric barrier-reefs, which have been gradually
converted into land by the accumulation of intervening mud-flats" (see
also Appendix II., page 287, to Darwin's "Coral Reefs," by T.G. Bonney,
Edition III., 1889.)) When reflecting in old days on the configuration
of our continents, the position of mountain chains, and especially on
the long-continued supply of sediment over the same areas, I used to
think (as probably have many other persons) that areas of elevation and
subsidence must as a general rule be separated by a single great line
of fissure, or rather of several closely adjoining lines of fissure. I
mention this because, when looking within more recent times at charts
with the depths of the sea marked by different tints, there seems to be
some connection between the profound depths of the ocean and the trends
of the nearest, though distant, continents; and I have often wished
that some one like yourself, to whom the subject was familiar, would
speculate on it.

P.S.--I do hope that you will re-urge your views about the reappearance
of old characters (498/2. See "Life and Letters," III., pages 245,
246.), for, as far as I can judge, the most important views are often
neglected unless they are urged and re-urged.

I am greatly indebted to you for sending me very many most valuable
works published at your institution.

2.IX.II. ICE-ACTION, 1841-1882.

LETTER 499. TO C. LYELL. [1841.]

Your extract has set me puzzling very much, and as I find I am better
at present for not going out, you must let me