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Letter 560

Darwin, C. R. to Milne-Home, David

20 [Feb 1840]

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    About earthquakes: the shock of February 1835 in Chile; possible connection between shocks occurring coincidentally in different parts of the world, and between earthquakes and the weather; DM's collection of accounts of earthquakes in Scotland.

Transcription

12 Upper Gower St

Thursday 20th

Sir

I much regret, that I am unable to give you any information of the kind you desire.— You must have misunderstood Mr Lyell concerning the object of my paper.— It is an account of the shock of Feb. 1835 in Chile, which is particularly interesting as it ties most closely together volcanic eruptions & continental elevations.— In that paper I notice a very remarkable coincidence in volcanic eruption in S. America at very distant places.— I have also drawn up some short tables showing, as it appears to me, that there are periods of unusually great volcanic activity, affecting large portions of S America.— I have no record of any coincidences between shocks there & in Europe.— Humboldt by his table in the Pers. Narrative (Vol IV. p. 36, English. Translat) seems to consider the elevation of Sabrina off the Azores, as connected with S. American subterranean activity: this connection appears to be exceedingly vague.—

I have during the past year seen it stated that a severe shock in the N. parts of S America coincided with one in Kamtschatka. Believing then that such coincidences are purely accidental—I neglected to take a note of reference,—but I believe the statement was somewhere in L'Institut for 1839.— I was myself anxious to see the list of the 1200 shocks alluded to by you,—but I have not been able to find out that the list has been published.—

With respect to any coincidences you may discover between shocks in S. America & Europe let me venture to suggest to you, that it is probably a quite accurate statement, that scarcely one hour in the year elapses in S. America, without an accompanying shock in some part of that large continent. There are many regions in which earthquakes take place every three & four days; & after the severer shocks, the ground trembles almost half-hourly for months.— If therefore you had a list of the earthquakes of two or three of these districts, it is almost certain some of them would coincide with those in Scotland, without any other connection than mere chance.—

My paper will be published immediately in the Geolog. Transactions.—& I will do myself the pleasure of sending you a copy in the course of (as I hope) a week or ten days. A large part of it is theoretical, & will be of little interest to you,—but the account of the Concepcion shock of 1835 will, I think, be worth your perusal.—

I have understood from Mr Lyell, that you believe in some connection between the state of the weather & earthquakes. Under the very peculiar climate of Northern Chile, the belief of the inhabitants in such connections can hardly, in my opinion, be founded in error.— It might possibly be worth your while to turn to p. 430 to 433 in my “Journal of Researches, during the Voyage of the Beagle”, where I have stated this circumstance.— On the hypothesis of the crust of the earth resting on fluid matter, would the influence of the moon, (as indexed by the tides), affect the periods of the shocks,—when the force which causes them, is just balanced by the resistance of the solid crust?

The fact you mention of the coincidence between the earthquakes of Calabria & Scotland, appears most curious.— Your paper will posses a high degree of interest to all geologists.— I fancied that such uniformity of action, as seems here indicated, was probably confined to large continents, such as the Americas. How interesting a record of volcanic phenomena in Iceland would be now that you are collecting accounts of every slight trembling in Scotland.— I am astonished at their frequency in that quiet country, as anyone would have called it.—

I wish it had been in my power to have contributed in any way to your researches on this most interesting subject, & begging you will excuse the length, with which I have ventured to address you.—

Believe me | Sir | With much respect | Yours faithfully | Chas. Darwin

    Footnotes Add

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    f1 560.f1
    The letter is endorsed in an unidentified hand: ‘March 20 1840’. If CD's ‘Thursday 20th’ is correct, the letter was written either in February or August 1840. However, August is excluded since the volume containing CD's paper ‘On the connexion of certain volcanic phenomena’ (Vol. 5, Part 3, of the Transactions of the Geological Society) was published before 27 June 1840 as a letter of that date at the Geological Society, which acknowledges receipt of the volume, testifies (John Thackray, archivist, personal communication). In view of CD's reference to the imminent publication of his paper, February would seem too early. It is probable, therefore, that CD wrote on Thursday 19 March and that 20 March was the date of receipt.
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    f2 560.f2
    ‘On the connexion of certain volcanic phenomena’Collected papers 1: 53–86.
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    f3 560.f3
    By ‘elevation’ CD means the actual emergence of the island from the sea. Humboldt's ‘vague’ connection is between the eruption of the volcano of Guadaloupe in 1796 and the appearance of Sabrina Island fifteen years later, in 1811 (Humboldt 1814–29).
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    f4 560.f4
    No such reference has been located in the issues of L'Institut for 1837–9. The footnote to this passage in ML 2: 114 refers to an article published in November 1840, after the presumed date of this letter. It is concerned with the relation between weather and earthquakes. No mention is made of South American earthquakes and Kamchatka. However, CD may have been referring to an article in Edinburgh New Philosophical Journal where Carl Gustav Christoph Bischof refers to simultaneous shocks felt at Ochotsk in Kamchatka and at Bogota (see Bischof 1839, p. 347).
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    f5 560.f5
    Eventually published as Milne 1841–4.
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