56 ME. H. W. MONCKTON ON THE 



thick beds of green sand absent, but patches and pockets of green 

 sand and even scattered green grains are wanting, yet these are all 

 usually found in Middle Bagshot sections. But Middle Bagshot 

 •without green sand would no doubt be so like Lower Bagshot that 

 perhaps we should fall back on the balance of probabilities ; now, 

 as the evidence of overlap elsewhere in this area has broken down, 

 when we find a bed resting on London Clay which may be Middle 

 or may be Lower Bagshot, I should say the balance is in favour of 

 its Lower Bagshot age, and I deny that such a statement involves 

 any petitio principii. 



This question takes us back to the Wellington College well. 

 Dr. Irving first described it in 1883,^ and again with further details 

 in 1885. On both occasions he described bed 14 as Bagshot or 

 partly Bagshot, and in 1885 said " we seem to find a passage from 

 the London Clay into the Bagshot Sands." ^ In his diagram in 

 1887,^ he put bed 14 into the London Clay without giving reasons. 

 He now says there is no evidence of a passage bed here.* 



In the note on page 145 of the Proc. Geol. Assoc, vol. viii, (1883) 

 he says that a new section of the first 30 feet of the well has been 

 opened, and the pebbles in bed 6 are more abundant than in bed 3. 

 But according to his figures bed 6 is 39 feet from the surface. I 

 mention these points to show what an unsatisfactory type-section 

 this is. One most important problem in connexion with this well- 

 section is the location of the bottom of the Middle Bagshot, taking 

 the Goldsworthy section as the type. Kow, looking at Dr. Irving's 

 latest account of the section (' Eecent Contributions,' p. 11), it 

 seems possible that the base of the Middle Bagshot is some 6 inches 

 below the top of bed 10, and that the clay and sand below should 

 be correlated with the Lower Bagshot of Goldsworthy. 



North-west of Wellington CoUege is the South Eastern Eailway, 

 where there are some sections which have been productive of 

 much discussion. The following diagrammatic sections along it have 

 been published : — 



1. 1883, Monckton, Quart. Journ. Geol. Soc. vol. xxxix. p. 351» 



Dip as stated in the note is too high, making Middle Bagshot 

 too thick ; outcrop of various beds fairly correct. 



2. 1883, Dr. Irving, Proc. Geol. Assoc, vol. viii. p. 150. 



3. 1885, Dr. Irving, Quart. Journ. Geol. Soc. vol. xli. p. 498. 



In both these the pebble-bed 3 is shown north of the station, 

 whereas I believe only debris of the pebble-bed occur there. 

 Anticlinals are shown north and south of the Wellington 

 College station wrongly, as I think. 



4. 1886, Monckton and Herries, Quart. Journ. Geol. Soc. vol. xlii. 



p. 407. The dip north of the station is rather too high, as 

 Dr. Irving has pointed out. The parts of the diagram 

 where there were no sections were left blank, but the pits 



^ Proc. Geol. Assoc, vol, viii. p. 144. 

 ^ Quart. Journ. Geol. Soc. vol. xli. p. 495. 

 3 Ibid. vol. xliii. p. 388, fig. 1. 

 '^ ' Eecent Contributions,' p. 12. 



