S. V. Wood, Jim. — Reply to Mr. James Oeikie. 1T3 



due to geograpliical causes, because the sliells and shell fragments 

 obtained by Mr. Jamieson in Aberdeenshire, although derivative in 

 the gravels in which they occurred, clearly show that the Crag fauna 

 once lived in Scotland, as we know that it also did still further 

 North in Iceland ; and, unless they have been wholly ploughed out 

 by the ice, such Crag beds may still exist in Aberdeenshire, concealed 

 by the Glacial formation. 



If it be asked why should not the East Anglian Glacial beds occur 

 in Scotland, and in the North and North-west of England, seeing 

 that all these parts partook of the same depression, the answer 

 appears to me a very simple one. When the period of maximum 

 depression was attained (which, as it seems to me, was about the close 

 of the contorted drift of Norfolk and Suffolk), the seaward edge of 

 the ice-sheet extended as far as the west of those counties ; and the 

 material degraded by that sheet always travelling outwards to this 

 edge furnished that which makes up this drift, which is principally 

 red sandy mud, and the soft chalk of the East Anglian counties 

 reconstructed into marl. After this deposit, the ice still further 

 extended, scooping in so doing some of the East Anglian valleys 

 out of this drift, and in South Suffolk nearly destroying it. At this 

 period the deposit thus resulting from the shedding of the outward 

 travelling material at the seaward edge of the ice was laid down 

 beyond our present shores, that edge being somewhere out in the 

 North Sea beyond the Suffolk and Norfolk coast. There then ensued 

 a continuous recession of the ice, the succeeding Middle and Upper 

 Glacial deposits going down into the valleys so excavated, without, 

 so far as I can see, any elevation or oscillation of level having occurred 

 until the Glacial period passed away, when, but not until when, 

 emergence took place.^ Wherever the ice-sheet rested, there I con- 

 tend no deposit occiirred, the material produced by its action inces- 

 santly travelling outwards to the ice edge, to be there deposited in 

 the manner shown by Mr. Archibald Geikie in his Memoir in 

 the Transactions of the Glasgow Geological Society for 1863, the 

 material nearest the edge being deposited in an unstratified condition, 

 from which it shaded off into first the streaked and obscurely stra- 

 tified, and further out into the stratified condition. Thus I conceive 

 the deposits succeeding the Contorted Drift have their sequence only 

 partly in the vertical and mainly in the horizontal direction ; the 



1 Mr. De Eance argues that the Lower Boulder-clay of Lancasbii-e must have 

 been deposited under a submergence of only about 100 feet beneath the present sea 

 level, because in it are fragments which he traces from rocks to the north of it, which 

 stand at elevations of only 300 feet. If, however, as I believe, the depression of that 

 period, instead of being 100, was upwards of 1500 feet, the ice-sheet blocking out the 

 sea and resting on these 300 feet elevations would convey fragments from them into 

 the Boulder-clay then forming at the seaward edge of the ice. In a similar way, I 

 now believe that the debris of the Chalk was carried into the great Chalky Clay when 

 the highest elevations of the Chalk country were below the sea level, and that the 

 second representation of my triple section, at p. 90 of the 24th Volume of the 

 Geological Society's Journal, instead of being drawn to the 700 feet level, might, by 

 thickening the ice-sheet, be drawn to the same 1500 feet level as the third, the 

 resulting phenomena being due to the retreat of the ice alone without additional 

 subsidence. 



