Yol. 69.] AGE OF THE SUFFOLK VALLEYS. 619 



far south as Wood supposed. Taken as a whole, however, AVood's 

 foundations were well and truly laid, and his successors may safely 

 build on them. 



The question of the origin of the valley-system of East Anglia 

 should be studied as a whole, and over as wide an area as possible. 

 If it were possible to ascertain the conditions obtaining in one 

 part of the region, it would not be unreasonable to draw conclusions 

 as to what was going on at the same time in another. The facts 

 to be observed in Norfolk, where the evidence was clearer, might 

 therefore throw light on those adduced by the Author from the 

 sister county. 



In the speaker's opinion, East Anglia was twice invaded by ice; 

 and first from the north, by the Great Scandinavian glacier. To 

 this invasion was due, not only the Contorted Drift of the remark- 

 able and abrupt ridge which crosses the north-eastern portion 

 of Norfolk from west-south-west to east-north-east, attaining a 

 maximum thickness of 300 feet, but also the uncontorted beds of 

 brick-earth equivalent to it which occur over the lower and flattened 

 region towards Norwich. The latter, the speaker considered, repre- 

 sented the moraine profonde of the North-Sea ice during its 

 maximum extension ; the former (the contorted part) a terminal 

 moraine at some stage of its retreat. 



Now, it seems clear that when the North-Sea ice crept over the 

 country from the Cromer coast to the latitude of the Waveney 

 Valley and beyond, the present valley-system of East Norfolk could 

 hardly have been in existence : any pre-Glacial elevations then 

 existing would have been levelled down by the ice, and any pre- 

 Glacial depressions levelled up, or filled in by the morainic detritus 

 brought by it. Moreover, the North-Sea Boulder Clay never occurs ' 

 in this region as a valley-deposit ; on the contrary, the valleys, as, 

 for example, those of the Yare and Wensum at Norwich, and of the 

 Waveney at Beccles, are distinctly shown to have been cut out of it. 



The second invasion, possibly separated from the first by a con- 

 siderable interval, was that of the great inland glaciers from the 

 north-west, to which the Chalky Boulder Clay, with its Neocomian 

 and Jurassic detritus, was due. The latter not only overspreads 

 the higher ground, but, as we all know, wraps the sides of the 

 present valleys, descending to the bottom, sometimes considerably 

 below sea-level. 



The excavation of the Norfolk valleys took place, therefore, after 

 or during the retreat of the North-Sea ice-sheet, but before the 

 deposition of a part at least of the Chalky Boulder Clay. It may 

 have been due, not improbably, to the action of torrential water 

 during the retreat and melting of the ice of the first glaciation. 



The Author had found similar conditions in Suffolk, as Wood 

 and the speaker did when they were mapping the county in the 

 sixties ; but here the relation of the Chalky Boulder Clay to the 

 North-Sea Drift, is not so clear, owing to the absence of the latter 

 from a great part of the county. This subject was dealt with in a 

 paper which the speaker read before the Society in 1866. 



