My dear Lyell

I have come here for a fortnights hydropathy, as my stomach had got from steady work into a horrid state. I am extremely much obliged to you for sending me Hartungs interesting letter.² The erratic boulders are splendid. It is a grand case of floating ice versus Glaciers.—³ He ought to have compared northern & southern shores of the islands. It is eminently interesting to me, for I have written a very long chapter on subject, collecting briefly all the geological evidence of glacial action in different parts of world, & then at great length, (on the theory of species changing) I have discussed the migration & modification of plants & animals in sea & land over a large part of world.⁴ To my mind it throws a flood of light on whole subject of distribution, if combined with the modification of species. Indeed I venture to speak with some little confidence on this, for Hooker about a year ago kindly read over my chapter,⁵ though he then demurred gravely to the general conclusion, I was delighted to hear a week or two ago, that he was inclined to come round pretty strongly to my views of distribution & change during the glacial period.⁶

I had a letter from Thompson of Calcutta the other day, which helps me much, as he is making out for me what heat our temperate plants can endure.—⁷ But it is too long a subject for a note; & I have written this only because Hartungs note has set the old subject afloat in my mind again. But I will write no more for my object here is to think about nothing, bathe much walk much, eat much & read much novels.—

Farewell, with many thanks & very kind remembrances to Lady Lyell.—⁸ | Ever yours | C. Darwin