Gunn — The Anglo-Belgian Basin. 159 



boulders are to be found to the extreme south-west of Devonshire 

 and elsewhere. I had found a boulder myself near Bovey Tracey, and 

 regarded it as a proof of the extension of northerly drift ; but Prof. 

 John Phillips informed me that it came from the neighbourhood of 

 Hay-Tor, and he expressed his opinion that during the G-laoial period 

 such ice-action might have been propagated from the heights of Hay- 

 Tor, to which the rounded eminence of that rock bears evidence. 



I do not think, therefore, that the discovery of striated boulders 

 and Boulder-clay to the south of the Dover chalk hills at all militates 

 against my theory, namely, that such a ridge of chalk formed a barrier 

 to the spread of Boulder-clay over France, and a way for the elephant, 

 etc., to have migrated into this country. 



Such was the main object of my paper. I propose in this, as a 

 sequel, to assign the probable boundaries of land on the north side. 

 Mr. Godwin- Austen, in his valuable article on the "Belgian Ter- 

 tiaries" (Quart. Journ. Geol. Soc. August, 1866, p. 240), represents the 

 opening between the Atlantic and Arctic Sea, and also Baffin's Bay, 

 to have been closed, while he leaves open the Straits of Dover. I 

 beg most respectfully to differ from him, both with respect to his 

 arrangement and distribution of land and sea on the north and on 

 the south : on the south for reasons already given ; and on the north 

 because it is scarcely possible, that with due regard to centrifugal 

 tendency, and the accumulation of ice and sea near the North Pole, 

 the waters could be so permanently and extensively hemmed in. 

 The reflux of accumulated ice and snow seems a necessary conse- 

 quence of the form and motion of the earth, and therefore I cannot 

 admit the probability of the exclusion of the Arctic Sea from the 

 Atlantic. But it appears to me that there was a considerable exten- 

 sion of land from the coast of Norway to the west, so as to mask this 

 country on the north, and serve as a defence against the flowing of 

 icebergs from the Polar regions ; and this extension of land appears to 

 account for the phenomena which present themselves to the geologist 

 from the Triassic to the Glacial epoch. 



I cannot resist the conclusion that icebergs charged with boulders 

 would have been borne from arctic to southerly regions ; and yet not 

 one instance of a scratched boulder during that enormous period of 

 time has, I believe, been found. This, I humbly submit, must be 

 due to such masking of this country between the North and the 

 Arctic Sea. No such boulders appear to have been imported into 

 Great Britain, and none appear during the level and warm condition 

 of this country, and of Europe generally, to have been propagated 

 within such territories. As the elevation of mountain ranges is seen 

 to be the cause of depression of temperature, so must the normal, or 

 level, state of the earth's surface be of a warmer and more genial 

 temperature ; and before we invoke extraordinary causes for the rise 

 of temperature, it would be well if attention were turned to what 

 would be the result of the absence of mountains or of hills, at least 

 above the permanent snow-line, and what would be the accumulating 

 effect of warmth, just as of cold. 



The great discovery by Professor Eamsay of signs of glaciation in 



