4 PROCEEDINGS OF THE GEOLOGICAL SOCIETY, 



Mr. J. H. Blake remarked that Dr. Irving, since he had given 

 up the theory of overlap on the southern side, had persistently at- 

 tempted to establish an overlap on the northern side of the London 

 Basin, but he had seen no evidence of this. All the evidence between 

 Ninemile Eide and Wokingham was in favour of Lower Bagshot. 

 The bed which Dr. Irving had claimed as the basement of the 

 Middle Bagshot in the Wokingham railway-cutting was considered 

 by the speaker to be an alteration of the Lower-Bagshot Beds, due 

 to the capping of gravel, and he saw no evidence of Middle Bagshot 

 at Wokingham. At Easthampstead Church was a characteristic 

 section of Lower-Bagshot Sands. He maintained the accuracy of 

 the original description of the Bagshot Beds by Prof. Prestwich in 

 1847, subsequently confirmed by the Geological Survey. 



Mr. Herries did not see much that was new in the paper. All 

 the arguments concerning the well at Ambarrow rest on assump- 

 tions as to constancy of thickness of the same strata. Within ten 

 minutes' walk of the sand-pit at Easthampstead Church were 

 exactly similar sands, which the Author had previously admitted to 

 be Lower Bagshot. 



Mr. Whitaker agreed with the Author to a certain extent con- 

 cerning mica, pipe-clay, and false-bedding, but the Author's 

 opponents did not rely on isolated pieces of evidence of such nature, 

 but rather on their combination. Not only had Prof. Prestwich 

 advanced the old view, it had been accepted by the earlier Surveyors, 

 and on later occasions other Surveyors had borne it out. With re- 

 gard to the clays underlying the pebble-beds at Bearwood, Dr. Irving 

 had originally described the pebble-beds as Upper Bagshot resting 

 on London Clay, but there was 30 feet of Lower-Bagshot Sand 

 below. At Bill Hill, Dr. Irving claimed the sand as Upper Bag- 

 shot ; nevertheless, there was green sand of the Middle Bagshot 

 higher up, either in place or but slightly moved. Dr. Irving's view 

 lauded us in great difficulties if we compared the northern and 

 southern sides of the London Basin, here only 7 or 8 miles apart, 

 for it supposed a different structure on those sides— a complicated 

 arrangement instead of a simple one. Dr. Irving ought to show 

 where these two different structures passed into one another on the 

 east and on the west. The occurrence of pebbles merely proved 

 that beds were somewhere between Woolwich and Headon horizons. 

 He held that the burden of the proof rested with the Author, and 

 he was afraid it was a burden greater than he could bear. 



The Author, in reply, maintained that you could, as a whole, 

 trace the green series, with its associated clays, through miles of 

 country. The clays, of which labelled specimens were on the table, 

 and which one speaker had stated to be non-existent, actually 

 occurred in open pits where it was stated that the Lower Sands crop 

 out. He had found reconstructed Middle-Bagshot clays over the 

 Lower Sands near Dowles Farm, and the section was dealt with in 

 the paper. He had based his arguments on relative levels to some 

 extent as giving data for measurements; but he had also paid 

 attention to similarities of lithological character. He had written 



