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Darwin Correspondence Project

To Leonard Horner   27 April [1855]

Down Farnborough Kent

Ap. 27th

My dear Mr Horner

I was regretting a year ago that I had not published a fuller account of the superficial beds,1 which I cd. have done from my M.S. but not being able to give any explanation, I cut the very little which I had to say to one paragraph at p. 143 of my Geolog. Obser. on Volcanic Isld.—2 I see I have not used the word vitrified, but I often have in conversation. I stated to you that one officer described the appearance as a stream of lava.— Another on coast of Australia said that the whole country seemed to have been fused by a flash of Lightning. These expressions will show what the appearance is.— You will see that my cases are in contact with Granite.— Rely on it, there is not, as Haidinger says, anything on earth to do with Heat.3

Pray forgive this hurried note: for it has chanced I have had to write several this morning.—

Believe me | My dear Mr. Horner | Yours very sincerely | C. Darwin


The superficial ferruginous beds at King George’s Sound, south-western Australia, as mentioned in letter to Leonard Horner, 18 [March 1855].
In his notes on the geology of places visited during the Beagle voyage, CD attributed the origin of these beds to mechanical violence at the time of deposition (DAR 38.1: 867 v.), a view which he repeated in Volcanic islands, p. 143. His point is that although the appearance might indicate some previous chemical fusion under the influence of heat, the origin was actually mechanical.
Wilhelm Karl Haidinger, director of the mineralogical collection in Vienna, had described the minerals collected on Joseph Russegger’s expedition (Russegger 1841–8, 3: 281). See letter to Leonard Horner, 18 [March 1855].


Regrets that he has not published his information on superficial beds except in abbreviated form, on p. 143 of Volcanic islands.

Letter details

Letter no.
Charles Robert Darwin
Leonard Horner
Sent from
Source of text
Lady Lyell (private collection)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 1676,” accessed on 28 April 2017,

Also published in The Correspondence of Charles Darwin, vol. 5