1884.] Construction of a Cliapter in the History of the Earth. 193 



And further, as in every case the pal83ontological evidence indicates that 

 these glacial beds are of late Palaeozoic or early Secondary age, I think 

 it is probable that, as has been suggested by Mr. H. F. Blanford, they 

 are of the same age as the Permian boulder clays of Europe.* 



Having thus obtained a common era in the geological history of 

 these three countries (India, Africa, and Australia) , we are able to examine 

 their history in an intelligent manner. The first thing noticeable is that, 

 in Australia, at a period corresponding fairly to the Devonian, both the 

 fauna and the flora were, judged by European standards, of a Palaeozoic 

 type. Later on, probably in Lower Carboniferous times, there appears, 

 among species of Lepidodendron, Rhacopteris, and Galamites, which, in 

 Europe, are found in rocks of Carboniferous age, a single species of 

 Glossopteris, the forerunner of a newer flora destined to supplant the 

 older forms. In the Newcastle (Upper Carboniferous) beds, this flora has 

 completely ousted the older forms, and, as I have already noticed, shews 

 considerable relationship to that of the Damudas in India. Yet, if the 

 Talchirs and the Bacchus Marsh beds are really of contemporaneous 

 origin as was first suggested by Dr. Feistmantel, and if the Bacchus 

 Marsh and Hawskbury beds are also contemporaneous (and the presence 

 of traces of glacial action in all three is at least presumptive evidence 

 in favour of this conclusion), the Damudas must be of very much later 

 date than the Newcastle beds, and we have to explain why it is that 

 the Newcastle flora left Australia when it did, and why it or its descen- 

 dants lingered on in India, and, as I propose to shew, spread over what 

 is now the Old World producing important modifications in its flora. 



It is possible to suppose that the Newcastle flora required a warm 

 — though from internal evidence one would rather look upon it as indi- 

 cating a cool temperate — climate ; that, on the advent of more severe con- 

 ditions, it migrated towards the Equator and remained there, not merely 

 through a period of extreme severity, but through a further period, when 

 the climate was cooler than it had been during the deposition of the 

 Newcastle beds, and during which a flora more suited to the latitude 

 flourished in Australia. But there are so many objections to this hj^po- 

 thesis that it can hardly be tenable, and, however wild my alternative 

 hypothesis may be thought, I hope to prove that it is really the more 

 probable of the two. 



In the first place, we have to account for the prevalence of glacial 

 conditions at a low level in India even within the tropics. This was not 

 paralleled during the last glacial period, for even the erratics of the 

 Petwar are 10 degrees beyond the tropics and 2,000 feet above the level 



* This correlation of tho Indian, African, and European boulder beda has been 

 suggested by Mr. H. F. Blanford, C^. J. G. S., XXI, p. 519. 



