348 SECTIONAL TRANSACTIONS.— C. 



in view of the unconsolidated nature of the sea bottom, that the whole of 

 the submarine relief discussed here may be due to currents at present in 

 operation. 



Mr. A. Austin Miller. — Pre-glacial erosion surfaces round the Irish 

 Sea coast. 



The pre-glacial surface is much obscured by thick accumulations of drift 

 on the lowlands and considerably modified by ice erosion on the highlands, 

 but sufficient evidence survives to permit an analysis of slopes and drainage 

 systems with a view to determining the base levels to which they are graded. 

 A correlation is attempted of evidence collected from the Irish Plain, the 

 Wicklow Mountains, North Wales, the Lancashire Plain and the Lake 

 District. 



Three erosion cycles are recognised, and the features correlated with each 

 cycle are separated and described. The obliteration of much of the evidence 

 by glaciation and its interference with such as survives forbids any precision 

 in assessing the earlier base levels, but they appear to indicate successive 

 sea-levels at about 600 ft., 400 ft. and 200 ft. above that of to-day. 



Dr. S. E. Hollingworth. — Platforms around the Lake District. 



The Lake District and its environs form a well-defined structural and 

 topographic unit bounded by sea on three sides. The superimposed radial 

 drainage has been considered to have developed on domed Mesozoic or 

 Tertiary rocks covering an old planation surface. 



Several well-defined plateaux or platforms have been cut in the varied 

 rocks beneath this surface of planation. 



Investigation in the field and by means of projected profiles, etc., revealed 

 additional evidence suggestive of the presence of a number of variably 

 developed platforms at intermediate and higher levels. This increase in the 

 number and frequency of possible platform levels made the danger of faulty 

 linking-up, by invoking or overlooking warping, very real. 



It became necessary to subdivide the area into narrow, more or less radial 

 strips, and investigate each separately. Results appear to indicate that 

 individual levels persist around the Lake District, thus excluding any 

 considerable tilting (except possibly accentuation of doming) since the 

 formation of the highest (2,600 ft. O.D.) platform. Watershed profiles yield 

 confirmatory results. 



Within the less glaciated valleys the ' valley within valley ' character is 

 often recognisable and may in exceptional cases be linked with steps in the 

 valley floor. 



In the more severely glaciated valleys, some steps that have developed by 

 ice-plucking, probably originated at limits of rejuvenation ; and some 

 correlation between these is possible. 



The recognition of the platforms in a heavily glaciated area appears to 

 give a definite limit to the amount of ice erosion. 



The platforms cut on the outer slope of the dome are considered to be of 

 marine origin with subaerial equivalents inland. They probably date from 

 early Pliocene or late Miocene times. 



Many cols correspond with platform levels and some river captures 

 appear to be associated with rejuvenations that followed the uplift of 

 particular platforms. Throughout the area glacier-lake overflows across 

 spurs tend to occur at the inner edge of platforms. 



Many of the platforms can be plausibly linked with others farther afield 



