234 Prof. Hughes, Criticism of the Geological [Oct. 30, 



to the conclusion that not only were the examples of striated 

 boulders in those rocks of doubtful origin, but that the negative 

 could be proved, and I laid upon the table of the Society a 

 series of examples in proof of the contention that these at any rate 

 must all be referred to other causes than ice action. 



I showed that the ancient deposits in which evidence of glacial 

 action had been observed in India, Africa and Australia, viz. the 

 Talchir, Karoo, and Marsh Bush beds, belonged to one geological 

 period, and occurred round one geographical basin. But I sub- 

 mitted that the evidence of their glacial origin, though cumulative, 

 was not sufficiently precise and mostly amounted to no more than 

 an impression derived from their general appearance, rather than 

 a proof in particular cases, and that there was not sufficient 

 evidence as to their mode of formation. Admitting the glacial 

 origin of some of them, I urged that the occurrence of boulder 

 clays did not imply that there had been extreme cold over the 

 areas where they were now found but that many such deposits 

 were transported by icebergs and other agents from the area of 

 glaciation. I pointed out that the beds in question occurred in 

 areas of known earth movement on an enormous scale, so that 

 regions which must have been glaciated when at a great elevation 

 must often have been afterwards depressed below sea-level. I 

 further maintamed that, even if the glacial origin of all these beds 

 were to be proved, that fact would lend no support to the theory 

 of circumpolar glaciation seeing that this basin lay entirely in 

 equatorial and temperate regions, some being north, some south 

 of the equator and, far from being circumpolar, did not touch 

 arctic regions at all. 



In like manner our well-established Pleistocene glaciation 

 occuri'ed round a basin, in a general way coinciding with the 

 Atlantic basin of to-day, but in no sense circumpolar. 



The evidence offered by Reusch of Palaeozoic glaciers in 

 Norway, although, if established, it would prove the repetition of 

 the phenomena does not help to settle the question of the relative 

 importance of the geographical and astronomical causes, as the 

 region in which they occurred is within the area of glaciation at 

 the present time. 



The question thus becomes reduced to a simpler form. It is 

 stated by those who refer the recurrence of glacial conditions to 

 extra-terrestrial causes that certain astronomical combinations 

 must have produced an effect on climate, now intensifying the 

 cold over one hemisphere now over the other, and if traces of 

 these alternations cannot be detected in the strata of the earth's 

 crust, it must be attiibuted to the imperfection of the record or 

 the incompleteness of the observations. 



Let us leave it so. But, granting all that is here asked for, if 



