THE BAGSHOT BEDS OP THE LONDON BASIN. 



391 



absent on duty at Devonport. That officer writes: "I cannot 

 make out a case for erosion or overlap." In the present paper the 

 Author had changed his tactics, and was endeavouring to establish 

 the overlap by means of an attenuation of the Lower Bagshot Beds 

 towards the margin of the basin. The evidence brought forward 

 was not satisfactory. There are most undoubted clay-beds of con- 

 siderable importance in the Lower Bagshot. A very remarkable 

 one is now being exposed in continuation of the Walton cutting 

 described last year. The base of this may be about 30 ft. up in the 

 Lower Bagshot series. On or about the same horizon is the brick- 

 earth of Hatch, between Addlestone and Chertsey, marked as Middle 

 Bagshot in the Survey Map ; this presents some very curious 

 features. He fully agreed with Mr. Irving's interpretation of the 

 alleged presence of pebbles in the Lower Bagshots of St. Anne's 

 Hill. The pebble-beds of the Middle Bagshots were largely deve- 

 loped in the upper part of the hill, and these had fallen over in 

 large masses. Still the absence of pebbles in the Lower Bagshots 

 of this part of West Surrey could not be taken as evidence that 

 pebbles never occurred in the Lower Bagshots. 



Mr. Whitaker missed the apocrenic acid of previous papers. Mr. 

 Hudleston had partly anticipated the substance of his remarks with 

 reference to the non-occurrence of pebbles in the Lower Bagshot. We 

 must bear in mind that pebble-beds occupy but a very small part of 

 the country. In Essex there are quantities of pebbles in the Lower 

 Bagshots. In Hampshire pebble-beds over large areas are most 

 distinctly capped by Bracklesham beds, and sometimes cut right 

 down to the London Clay. Sand and gravel are convertible terms. 

 He objected to the straight line shown between Chalk and Tertiary 

 beds on one of the sections, and spoke of the danger of drawing 

 sections from data yielded by a few borings. He thanked Mr. Irving 

 for again bringing forward the subject. 



The Author referred to the number of criticisms and the lateness 

 of the hour ; most of the points mentioned were dealt with in the 

 paper. He replied to Mr. Whitaker's remarks on the lines in his 

 sections. Having made a special study of the continental literature 

 on the subject, he would stand by his remarks on the humus acids : 

 the action of the humus acids had been of some importance in these 

 and other beds. He had proved that the Diatom-remains noticed by 

 him were not in a living state. It must be understood that this 

 paper was mainly confined to the northern side of the basin. He gave 

 reasons why he had drawn the anticlinal in the Wellington-College 

 section. Referring to certain of the pebble-beds mentioned in his 

 paper, and more especially to the criticisms of Messrs. Monckton 

 and Herries, he insisted upon the pebble-beds at Easthampstead and 

 other points (e. g. at Barkham) being in in situ. The remarks of 

 one of them showed that he had not mastered what the author had 

 already published on the evidence of well-sections. He further dis- 

 cussed the presence of marine shells in the Middle Bagshots, and 

 said that this was no more inexplicable than the presence of inter- 

 calated beds containing marine shells in other fluviatile and terres- 



