374 SECTIONAL TRANSACTIONS.— E. 



activity and thus afford a basis for a fundamental regional sub-division of 

 the chalk tracts. 



Mr. D. L. Linton. — The origin of the rivers of southern England (11.45). 



It has been known for some twenty-five years that certain of the Hamp- 

 shire rivers present anomalous and enigmatic relations to the structure of 

 the country through which they flow. Such streams as the Itchen, Meon 

 and Test flow directly across anticlinal ridges in a fashion which the workers 

 of that day found very difficult of explanation. At first they naturally 

 attempted to explain these puzzling features as modifications by capture 

 of a drainage system which had originally been in fair accord with the 

 structures, but as further examples of the phenomenon became known the 

 hypothesis seemed increasingly inadequate, and H. J. O. White tentatively 

 suggested that the rivers might have been superimposed from a tilted 

 surface on which the folds had been completely planed off. In 1932 the 

 writer attempted to apply this concept to the drainage of the whole Wessex 

 region, but though the hypothesis seemed able to explain the anomalous 

 features of the present rivers it was found necessary to assume that super- 

 imposition had taken place from a plane veneered by fluviatile gravels. 



Since that date further investigation has revealed other and similar 

 anomalous drainage features in Dorset and the Southern Weald which 

 seem to demand a similar explanation. It has, moreover, proved possible 

 to trace into the Wessex region the landform features, described in the 

 preceding communication, which are inseparably connected with the 

 Pliocene transgression. These permit us to believe that the Southern Weald 

 and all Wessex as far west as a coastline which passed somewhat north-west 

 of Basingstoke, Salisbury and Dorchester, was covered by the Pliocene sea, 

 and that it was upon its emerged floor that the present streams arose. 



The river systems are thus seen to afford a clue to the reconstruction of 

 an episode which on the one hand provides an invaluable datum in problems 

 of denudation chronology, and on the other can alone afford a rational basis 

 for the geographer's interpretation of the present landscape with its signifi- 

 cant and striking regional contrasts. Finally, the new evidence enables us 

 for the first time to perceive something of the importance of the Pliocene 

 phase in the evolution of the landscape of south-eastern England as a whole. 



Afternoon. ' 

 Tour of Nottingham. 



Friday, September 3. 



Presidential Address by Prof. C. B. Fawcett on The changing distribution 

 of population (lo.o). 



Dr. Vaughan Cornish. — On the apparent enlargement of the setting sun 



The great increase in the apparent size of the sun when sufficiently near 

 the horizon to be viewed together with the features of the landscape is a 

 phenomenon which has attracted general attention throughout the ages. 

 The customary explanation is that the largeness of the angle subtended by 

 .the disc is only fully appreciated when brought into comparison with 

 terrestrial objects. It would not be unreasonable to inquire whether under 



