Responds to Lyell's query [missing] about northern and southern limits of coral islands of the Pacific. Warns that coral islands are much more thinly distributed than people realise and cites examples. Comments on views of Matthew Flinders. Reading work of É[lie] de B[eaumont]. Notes difficulty of setting an east-west boundary to coral islands.
My dear Lyell
I cannot say what are the southern or northern limits of true coral islands in Pacific,
for scacely any islands occur south or north of the Tropic.— Bermuda in Lat
33o 1/2. is an exception to general rule owing to Gulf
Stream— Coral is abundant at Mauritius on Tropic & I believe at Loo
Choo a little north of T of Cancer (that is
23o 30’) It will be difficult for you to talk of great areas
abounding with corals.— People's ideas of the Pacific are most
false. — In the thick archipelagoes—in a long days sail, you
will often only see one or two islands. The Dangerous Archipelago is (speaking very roughly & accuracy cannot be obtained in such a
point) is an oblong of 1200 miles in length, by 300 or 400 in
breadth, which is thickly strewed with lagoon
The sea proposed by Flinders to be called the Corallian Sea, is bounded on East & West by Australian Barrier, & the great reefs of New Caledonia, & to the N. by the reefs of Louisiade.— This area thus surrounded on 3 sides by coral & containing a few reefs is about,— the dimension here given.—
600 1200 miles 1000 miles
But then the land to which these reefs are attached is primary.— I fear this information will scarcely be of any service to you; but it is the best I can give.— Many thanks for the books.— I am afraid I shall not be able to read them for nearly a week, as I have not finished E. de B.—
Yours very truly, C Darwin—
With respect to your E & W. Boundary of coral in the Pacific, it is scarcely possible to give any satisfactory answer for the two great areas, the Dangerous or Low Archipelago, and the Corallian sea are separated by great volcanic band, in which coral exists in very small quantity, or is entirely absent.—
- f1 394.f1The Ryuku Islands.
- f2 394.f2Tuamotu Archipelago in French Polynesia.
- f3 394.f3Ratak Chain, the eastern chain of the Marshall Islands.
- f4 394.f4Ralik Chain, the western chain of the Marshall Islands.
- f5 394.f5Matthew Flinders.
- f6 394.f6That is, it consists of the most ancient sedimentary strata. CD was concerned to correct the commonly held assumption that coral reefs are necessarily associated with volcanic formations. See Coral reefs, pp. 60–1.
- f7 394.f7A note in Lyell's hand reads ‘Mr
Darwin on Coral islands. thinly scattered over what area— Decr 1837.’ For Lyell's use of the information in this letter see his discussion: ‘Geographical extent of white chalk’ in C. Lyell 1838, chapter 15.
- f8 394.f8Probably Dufrénoy and Élie de Beaumont 1830. In CD's record of his reading (DAR 119) this work is listed as having been read at the end of 1837.