THE GLACIAL EPOCH. 39 



after the appearance of the cold that the species were changed from their southern tj'pe into northern 

 forms wc cannot tell. My view is that it would be soon ; but doubtless, as the cold increased and 

 advanced southwards, fresh boreal species woidd be developed b}^ the increase of the power of the 

 instrimient of change, and doubtless also on its decrease as well as its increase the same result would 

 follow. But what I maintain is, that until the cold began, boreal species there were none. I speak 

 not only of plants, but of shells, mammals, and ever}^ created thing. 



Some botanists speak of the plants returning in the same line of longitude after the retreat of 

 the glacial epoch as they had advanced before it. If my view is correct, this of course is impossible. 



Neither can I adopt Dr. Hooker's view of the course of action of the glacial cold in Greenland, 

 and its probable effect upon " the survivors," for two reasons, the one that Greenland in all pro- 

 babilit)' had not then its present configuration, but was united to Europe ; the other, that, supposing 

 it not to have been so, then I cannot conceive to be possible that there should have been (?«y 

 survivors. It seems a physical impossibility that any germ of life could have sui'vived the euvelope- 

 ment of the soil for thousands of years, with a thick coating of ice, which was certainly the con- 

 dition of the whole northern hemisphere to a far more southerly latitude than Greenland. 



When the glacial epoch arrived and advanced southwards, it must have operated in two 

 waj's — it must either have killed, or transformed into something else, all those species of plants 

 and animals which were subjected to its influence. It is also possible that it may have driven before 

 it, at a respectfid distance, all those which escaped its influence, and which migrated southward, 

 carrying their climate with them ; but as a uniform climate had imtil then subsisted at least as far 

 south as Greece, as is proved by the fossil flora of Euboea, it is not necessary for our argument to 

 decide whether the old miocene flora still subsisted in the southern parts of Europe in virtue of that 

 having been the general and established flora of the coimtry, or if, imder the altered conditions of 

 climate, it was now confined to those parts where the temperature and other conditions of life 

 suited it. 



To this it is doubtless due that certain miocene genera, such as Clethra, Bystkopogon, 

 Cedronella, and Oreodaphxe, still subsist in the flora of Madeira and Porto Santo, and of the 

 Canaries and the Azores, as well as in North America. 



In either view there would, both in the Old World and the New, be a double band of species ; 

 the most southerly consisting of the old species which lived before the glacial epoch ; and next, a 

 more northerly band fringing the line of ice, consisting of what we now call Aljjine and Boreal 

 plants and animals, and which were developed out of the old species under the influence of the novel 

 sensation of cold. 



But although Dr. Hooker's explanation of the facts is not satisfactory to me, I readily accept 

 his facts themselves, and they show that, as already said, the type of the flora of Greenland is 

 European ; and if all life existing in Greenland previous to the glacial epoch was then exterminated, 

 it follows from their presence there now that it must have been connected with Europe subse- 

 quently to that epoch, for a sufiicient time to allow it to be refurnished with European plants 

 and insects. It is a necessity, not a matter of probabilitj*. 



Next, as Iceland, Greenland, and Spitzbergen,* all three possess nearly the same flora, and 

 that flora European, they must either have been united to each other and to Europe in one line, 

 or united by different necks of land to the Continent ; which latter supposition, altliough not irn- 



* There are some peculiarities in that of Spitzbergen to which I shall presently advert. 



