1857.] GODWIN-AUSTEN — BOULDER IN CHALK. 265 



period of the breaking up of the coast- ice arrives, great masses are 

 drifted away, bearing with them in their under surfaces compact 

 masses of frozen beach, which separates itself as the ice decays. 



We have only to imagine a case where a portion of such a floe, 

 so laden, should have wasted as it travelled into warmer regions, so 

 that it no longer retained sufficient buoyancy to float the mass of 

 boulders, shingle, and detritus attached to it ; and what remained 

 would then sink together, and become buried in whatever the sub- 

 stance of the sea-bed beneath the spot might happen to be. 



Geologists have long since become aware of the power of coast-line 

 ice as a moving agent : even in our climate and country its mode of 

 action is exhibited ; it may be well seen every winter over the north- 

 ern European area, whilst for its fullest powers, as displayed in high 

 northern regions, we have graphic pictures in the narrative of Dr. 

 Kane. I know of no other agent but that of coast-ice by which 

 a mass of incoherent materials could have been held together, as a 

 characteristic portion of a sea-beach, and so deposited at a vast 

 distance from the nearest land. Such, 1 conclude, was the nature of 

 the agency by which the assemblage discovered in the chalk at 

 Purley was kept together and conveyed. 



Form and composition of the Land of the Cretaceous Period. — 

 The upper Mesozoic group (cretaceous) in its northern expansion 

 outspanned the limits of the lower Mesozoic (oolitic). We have 

 abundant evidence that strata of Great Oolite and Oxford Clay entered 

 into the coast-line of the Lower Greensand sea ; but the materials 

 carried into the area of the chalk-deposit have as yet consisted mainly, 

 if not exclusively, of Crystalline and Palaeozoic formations. 



Such was the character of the dry land which bounded the cre- 

 taceous gulf or bay extending west from the Cotentin, across our 

 south-eastern area, towards Sweden. 



It remains only to notice, and that most cursorily, the composition 

 of those areas of land which existed as such at the time of the greatest 

 extension of the Cretaceous ocean, and which continue as such at the 

 present time. 



On the west the cretaceous strata of Noirmoutier indicate littoral 

 conditions, as also do those of Aix (oolitic) or Charentelnferieure. Such 

 is the case also with respect to the sands, shingle-beds, and calcareous 

 strata of the Cotentin. The intervening country between these two 

 localities, which forms the western district of France, consists of 

 gneissic and granitic rocks, with old sedimentary slates and sandstones 

 (quartzite). The west of England is similarly composed. We may 

 place the whole of the area between these two adjoining peninsulas 

 in the condition of land-surface at the end of the Cretaceous period, 

 and may extend this old land far into the present Atlantic area. 



The small outlier of Cretaceous sand near Bideford shows that the 

 Cretaceous sea must have had an extension considerably to the west 

 of its present limits. The course of the outline of this sea across our 

 island may be passed over for the present, as the extraneous materials 

 in the White Chalk do not resemble any of the crystalline rocks of our 

 series. In the south of Sweden, on the contrary, the cretaceous beds 



