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 and four days; and 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 that 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 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, and 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 and earthquakes. Under the very peculiar climate of Northern Chile, the belief of the inhabitants in such connection can hardly, in my opinion, be founded in error. It must possibly be worth your while to turn to pages 430-433 in my "Journal of Researches during the Voyage of the 'Beagle'," where I have stated this circumstance. (479/3. "Journal of Researches into the Natural History and Geology of the Countries visited during the Voyage of H.M.S. 'Beagle' round the World." London, 1870, page 351.) 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 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. LETTER 480. TO L. HORNER. Down, August 29th [1844].