354 Rev. A. Irving — The Broohwood Well-Section. 



sandy materials washed down from the sandy strata situated at 

 higher levels on the slopes of the valley. 



In attempting to classify the Bagshot Beds I have used the 

 grouping adopted in descriptions recently published of other deep- 

 well sections l in the Bagshot District (those namely at Wellington 

 College, Farnborough and Mytchett), and for the reasons there given. 

 A comparison of this section with those brings out a very remark- 

 able continuity in the general characters of the Middle and Lower 

 Bagshot Beds, though there is just that amount of variation in details 

 which we should be led to expect from the conditions under which 

 they appear to have been deposited. 2 I have found it by no means 

 easy to draw a line between the Lower Bagshot Beds and the London 

 Clay, for there is no abrupt transition from one to the other, in the 

 description given below ; while a careful study of the actual speci- 

 mens leaves no alternative that I can see to the recognition of a 

 gradual passage upwards from the London Clay to the characteristic 

 Lower Bagshot Sands. The resemblance of what is seen here to 

 what is seen in the specimens from about the same horizon in the 

 Wellington College well-section is very close indeed ; and is in 

 striking contrast with the abrupt transition between the two forma- 

 tions which I have observed in sections already described at Aldershot, 

 Wokingham, and Bracknell, on the marginal portions of the area. 



The following points in connection with this section (see p. 355) 

 appear to me worthy of note. 



1. The apparent gradual passage from the London Clay into the 

 Lower Bagshot Sands, as contrasted with the abrupt transition 

 observable in the Walton section recently described by Mr. Hudle- 

 ston, 3 and in those on the marginal portions of the Bagshot area to 

 which I have referred above. 



2. The remarkable absence of any considerable development of 

 clays, the entire absence of all record of pebbles, and the general 

 predominance of quartz sand stained by carbonaceous matter of 

 vegetable origin are characters which the Lower Bagshot beds of 

 this section possess in common with the Lower Bagshot strata of 

 three deep- well sections, of which I have given a fuller account else- 

 where, 4 and to which I have referred above. 



3. The specimens of the slightly loamy sands which occur in this 

 section between the depths of 68 and 143 feet bear a striking re- 

 semblance to those which occupy about 92 feet of the Lower Bag- 

 shots in the section at Wellington College. This resemblance comes 

 out very strongly when the specimens from the two places are 

 directly compared. 



4. Of the pyrites found in the Bagshot Sands one large heavy 

 specimen (found at the depth of 130 feet) and many smaller 

 ones are preserved. They are quite un weathered, and are probably 

 pyritized wood in situ ; but with the cement stones found in the same 

 beds the case is different. They are very much weathered, their 



1 Q.J.G.S. loc. cit. 



2 Cf. Q.J.G.S. loc. cit. ; also Geol. Mag. Dec. III. Vol. II. p. 25. 



3 Q.J.G.S. April, 1886. i Q.J.G.S. loc. cit. 



