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"12 Upper Gower Street, London,

"March 20th, 1840.

"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 February 1835 in Chili, which is particularly interesting, as it ties most closely together volcanic eruptions and con- tinental elevation. In that paper I notice a very remarkable coincidence in volcanic eruptions in South 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 South America. I have no record of any coincidence between shocks there and in Europe. Humboldt by his table seems to consider the elevation of Sabrina off the Azores as connected with South American subterranean activity. The connection appears to me exceedingly vague. I have, during the past year, seen it stated that a severe shock in the north parts of South America coincided with one in

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Kamatschka. Believing, then, that such coincidences were purely accidental, I neglected to take a note for reference, but I believe the statement was made 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 South America and 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 South America without an accompanying shock in some part of that large continent. There are many regions in which earthquakes take place every three or four days, and after the severer shocks the ground trembles almost for months. If, therefore, you had a list of the earth- quakes 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 Geological Transactions, and I will do myself the plea- sure of sending you a copy in the course of—as I hope— a week or ten days. A large part of it is theoretical, and will be of little interest to you, but the account of the Conception 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 and earthquakes. Under the very peculiar climate of Northern Chili, the belief of the inhabitants in such

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connection can hardly, in my opinion, be founded in error. It might possibly be worth your while to turn to page 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 earthquake of Calabria and Scotland appears most curious. Your paper will possess 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 any one 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, with much respect, yours faithfully, Chas. Darwin."