430 NATURAL SCIENCE. dec, 



material shorewards, and throws it up sometimes out of its ownr 

 reach. In a subsiding area, material might in this way be worked 

 up a considerable distance above its original level. I beHeve the sea 

 alone is capable of doing this, but assisted by shore-ice it would be 

 more efficacious, and Avould account for some of the striations on the 

 stones. 



The material in which the erratic stones is embedded is unmis- 

 takably shore sand. 



The sand of Tryfaen could not have come from anywhere but the 

 sea itself. It also has been worked uphill, for there is no local 

 material to yield it, and the wear and polish of the grains are distin- 

 guishingly marine features. 



To anyone who has paid attention to this part of the subject, its 

 marine character is unmistakable. The rocks that have been worked 

 uphill are, as a rule, water-worn and rounded. 



2. — The High-level Shelly Drift is partial and sporadic. 



If the high-level drift were due to submergence, say the land-ice 

 theorists, we should find it all over the hills, whereas it is confined to 

 a few elevated places. This seems to me to be a singular argument. 

 According to the postulate, the whole of the Drift above sea-level has 

 been pushed up. Lancashire and Cheshire are pretty nigh covered 

 with Drift. So much so, that almost every boring made into the solid 

 rock through it involves more or less change in the mapping of the 

 Triassic beds. 



This is no disgrace to the surveyors who mapped them; they could 

 not see through the Drift — even if Drift-geologists can ? If, then, the ice- 

 sheet only leaves sporadic deposits, why is not the Drift to the height 

 of, say, 400 feet sporadic instead of continuous ? Whether placed 

 there by an Irish-Sea glacier or by the sea itself, both high-level and 

 low-level Drift obey the laws of gravitation, consequently the most 

 material is found at the lower levels. 



In working out this objection, the supporters of the Irish-Sea 

 glacier unconsciously minimise the quantity of high-level Shelly Drift 

 — there is much more in existence than they have persuaded them- 

 selves to believe. There is no occasion for me to name the localities 

 over again, as I have stated them at the commencement of this paper. 

 Again, it can hardly be expected that all high-level deposits laid down 

 by the sea should contain shells, and further it is not philosophical to 

 assume that all high-level shelly drifts have been discovered. Their 

 discovery has generally been in the nature of an accident. I fear the 

 advocates of the Irish-Sea glacier are continually forgetting how 

 difficult it is to prove a negative, and, unfortunately, their arguments 

 are too frequently of the negative kind. 



But, whether laid down by an Irish-Sea glacier or by the sea, the 

 high-level drifts have been subjected to very active denudation 

 since, as the rainfall is much greater in these elevated localities than 



