1858.] FLOATING ICE. 113 



horrid state. I am extremely much obliged to you for send- 

 ing me Hartung's interesting letter. The erratic boulders are 

 splendid. It is a grand case of floating ice versus glaciers. 

 He ought to have compared the northern and southern shores 

 of the islands. It is eminently interesting to me, for I have 

 written a very long chapter on the subject, collecting briefly 

 all the geological evidence of glacial action in different parts 

 of the world, and then at great length (on the theory of species 

 changing) I have discussed the migration and modification of 

 plants and animals, in sea and land, over a large part of the 

 world. To my mind, it throws a flood of light on the whole 

 subject of distribution, if combined with the modification of 

 species. Indeed, I venture to speak with some little con- 

 fidence on this, for Hooker, about a year ago, kindly read 

 over my chapter, and 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 and change during the glacial period. 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. But it is too long a subject for 

 a note ; and I have written thus only because Hartung's note 

 has set the whole 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, and read much 

 novels. Farewell, with many thanks, and very kind remem- 

 brance to Lady Lyell. 



Ever yours, 



C. Darwin. 



Darwin to Mrs. Darwin. 



Moor Park, Wednesday, April [1858]. 

 The weather is quite delicious. Yesterday, after writing to 

 you, I strolled a little beyond the glade for an hour and a half, 

 VOL. 11. I 



