1843— 1882] GLACIAL PERIOD 477 



means follows, I think, that there may not have been formerly Letter 363 

 gigantic glaciers on the eastern and more humid side. 



In the third edition of Origin, p. 403, 1 you will find a brief 

 allusion, on authority of Mr. D. Forbes, on the former much 

 lower extension of glaciers in the equatorial Cordillera. Fray 

 also look at page 407 at what I say on the nature of tropical 

 vegetation (which I could now much improve) during the 

 Glacial period. 2 



I feel a strong conviction that soon every one will believe 

 that the whole world was cooler during the Glacial period. 

 Remember Hooker's wonderful case recently discovered of 

 the identity of so many temperate plants on the summit 

 of Fernando Po, and on the mountains of Abyssinia. 3 I look 

 at [it] as certain that these plants crossed the whole of Africa 

 from east to west during the same period. I wish I had 

 published a long chapter written in full, and almost ready for 

 the press, on this subject, which I wrote ten years ago. It 

 was impossible in the Origin to give a fair abstract. 



My health is considerably improved, so that I am able to 

 work nearly two hours a day, and so make some little 

 progress with my everlasting book on domestic varieties. 

 You will have heard of my sister Catherine's easy death 4 last 

 Friday morning. She suffered much, and we all look at her 

 death as a blessing, for there was much fear of prolonged and 

 greater suffering. We are uneasy about Susan, 5 but she has 

 hitherto borne it better than we could have hoped. 



1 Origin, Ed. vi., p. 335, 1882. " Mr. D. Forbes informs me that he 

 found in various parts of the Cordillera, from lat. 13 W. to 30 S., at 

 about the height of twelve thousand feet, deeply furrowed rocks . . . and 

 likewise great masses of detritus, including grooved pebbles. Along this 

 whole space of the Cordillera true glaciers do not now exist, even at 

 much more considerable height." 



3 "During this, the coldest period, the lowlands under the Equator 

 must have been clothed with a mingled tropical and temperate vegeta- 

 tion. . . ." {Origin, Ed. VI., 1882, p. 338). 



3 "Dr. Hooker has also lately shown that several of the plants living 

 in the upper parts of the lofty island of Fernando Po, and in the neigh- 

 bouring Cameroon Mountains, in the Gulf of Guinea, are closely related 

 to those on the mountains of Abyssinia, and likewise to those of temperate 

 Europe" {he. tit., p. ^yj). 



* Catherine Darwin died in February 1866. 



5 Susan Darwin died in October 1866. 



