482 GEOGRAPHICAL DISTRIBUTION [Chap. VI 



Letter 365 Catalogue} but must buy it, if it gives the facts about rare 

 plants which you mention. 



And now I have given more than enough of my notions, 

 which I well know will be in flat contradiction with all yours. 



Wollaston, in his Insecta Maderensia? 4to, p. 12, and in 

 his Variation of Species, pp. 82-7, gives the case of apterous 

 insects, but I remember I worked out some additional details. 



I think he gives in these same works the proportion of 

 European insects. 



Letter 366 To J. D. Hooker. 



Sir Joseph had asked (July 31st, 1866): " Is there an evidence that 

 the south of England and of Ireland were not submerged during the 

 Glacial epoch, when the W. and N. of England were islands in a glacial 

 sea? And supposing they were above water, could the present Atlantic 

 and N.W. of France floras we now find there have been there during the 

 Glacial epoch ? — Yet this is what Forbes demands, p. 346. At p. 347 

 he sees this objection, and wriggles out of his difficulty by putting the 

 date of the Channel 'towards the close of the Glacial epoch.' What 

 does Austen make the date of the Channel ? — ante ox post Glacial ? " The 

 changes in level and other questions are dealt with in a paper by R. A. C. 

 Austen (afterwards Godwin-Austen), " On the Superficial Accumulations 

 of the Coasts of the English Channel and the Changes they indicate." 

 Quart. Journ. Geol Soc., VII., 185 1, p. 118. Obit, notice by Prof. Bonney 

 in the Proc. Geol. Soc., XLI., p. 37, 1885. 



Down, Aug. 3rd [1866]. 



I will take your letter seriatim. There is good evidence 

 that S.E. England was dry land during the Glacial period. 

 I forget what Austen says, but Mammals prove, I think, that 

 England has been united to the Continent since the Glacial 

 period. I don't see your difficulty about what I say on the 

 breaking of an isthmus : if Panama was broken through would 

 not the fauna of the Pacific flow into the W. Indies, or vice 

 versa, and destroy a multitude of creatures? Of course I'm 

 no judge, but I thought De Candolle had made out his case 

 about small areas of trees. You will find at p. 112, 3rd edit. 

 Origin, a too concise allusion to the Madeira flora being a 

 remnant of the Tertiary European flora. I shall feel deeply 

 interested by reading your botanical difficulties against 



1 Probably the Catalogue of the Coleopterous Insects of the Canaries 

 in the British Museum, 1864. 



3 Insecta Maderensia, London, 1854. 



