18461878] MISCELLANEOUS 223 



fear I shall not be able to give any assistance to Book 1 1 1. 1 Letter 557 

 I think I formerly gave my few criticisms, but I will read 

 it over again very soon (though I am striving to finish my 

 S. American Geology 2 ) and see whether I can give you any 

 references, I have been thinking over the subject, and can 

 remember no one book of consequence, as all my materials 

 (which are in an absolute chaos on separate bits of paper) 

 have been picked out of books not directly treating of the 

 subjects you have discussed, and which I hope some day to 

 attempt; thus Hooker's Antarctic Flora'* I have found emi- 

 nently useful, and yet I declare I do not know what precise 

 facts I could refer you to. Bronn's Geschichte^ (which you 

 once borrowed) is the only systematic book I have met with 

 on such subjects ; and there are no general views in such 

 parts as I have read, but an immense accumulation of refer- 

 ences, very useful to follow up, but not credible in themselves : 

 thus he gives hybrids from ducks and fowls just as readily 

 as between fowls and pheasants ! You can have it again 

 if you like. I have no doubt Forbes' essay, 5 which is, I 

 suppose, now fairly out, will be very good under geographical 

 head. Kolreuter's German book 6 is excellent on hybrids, 

 but it will cost you a good deal of time to work out any 

 conclusion from his numerous details. With respect to varia- 

 tion I have found nothing but minute details scattered over 

 scores of volumes. But I will look over Book III. again. 

 What a quantity of work you have in hand ! I almost wish 

 you could have finished America, and thus have allowed 

 yourself rather more time for the old Principles ; and I am 

 quite surprised that you could possibly have worked your 



This refers to Book III. of the Principles " Changes of the Organic 

 World now in Progress." 



( Geological Observations on South America was published in 1846. 



3 Botany of the Antarctic Voyage of H.M.S. "Erebus" and " Terror ' 

 in the Years 1839-43. ! Flora Antarctica. 2 vols., London, 1844-47. 



4 Naturgeschichte der drei Reiche. H. E. Bronn, Stuttgart, 1834-49. 

 "On the Connection between the Distribution of the existing Fauna 



and Flora of the British Isles, and the Geological Changes which have 

 affected their Area, especially during the Epoch of the Northern Drift," 

 by E. Forbes. Memoirs of Geological Survey ', Vol. I., p. 336, 1846. 



3 Joseph Gottlieb Kolreuter's Vorlaufige Nachricht von eininigen 

 das Geschlecht der Pflanzen betreffenden Versuchcn und Beobachtungen. 

 Leipzig, 1761. 



