158 ME. W. H. HUDLESTON ON A SECTION THROUGH 



Section at Sir RicJiarcVs Bridge. 



ft. in. 



The superficial beds (estimated) 17 



ft. in. 

 ["Yellow sand 5 



No. 1. Lower Baff shots... i c-u^ ^ ii j" ' "-Vi!." ' " i 



° bharp yellow sand with ochrey 



[ layers U 2 



i-^^-ciay {Sre".°.'.''.::::::;::;:::::::: 4 I ^^ 



Total 24 



IS'o. 1 is rather nipped here by the superficial beds*, but presently 

 acquires considerable thickness ; at the west end of the bridge it is 

 seen to be covered by No. 2, as shown in the figure. Originally this 

 bed may have overlapped N'o. 1, but there is now no trace of it east 

 of tbe bridge. One might as well try to diagnose the colour of a 

 chameleon as to describe 'No. 2 with any pretensions to absolute 

 accuracy. Speaking generally, it is a very dark sticky clay in thin 

 laminae : but it is so much permeated by sands of all colours, and 

 changes, within such short distances, to brown and red clays, with, 

 thin pans of iron-rust, that no single description will suffice. The 

 general eff'ect produced in section, by contrast with the sands above 

 and below, is a dark blue ; hence I call this bed, or series of beds, 

 the " Blue Bagshots." The average thickness is about 4 feet. 



Already, at the point where the London Clay falls below the level 

 of the permanent way, the Bagshots have attained a thickness of 

 10 feet, partly made up of No. 2, but principally owing to the great 

 expansion of jSTo. 1, which is very irregular and false -bedded, some- 

 times pinched by No. 2, and sometimes expanding suddenly. This 

 false-bedding frequently changes in direction, and especially on 

 either side of a thin seam of brown clay, as may be noticed in the 

 annexed sketch by Mr. Foord (fig. 6). A very few inches of No. 3, 

 which represents the main body of the Lower Bagshots hereabouts, 

 contributes to the total of 10 feet at this point. 



About 80 yards west of the centre of the bridge the Bagshots 

 attain their maximum tbickness in block C. This is made up as 

 follows : — 



ft. in. 



No. 3. Buff sands, partially laminated 4 2 



ft. in. 



No. 2. Upper clay 10 



Red sands 1 10 



Lower Blue Clay 12 3 10 



No, 1. (Base not seen) 3 



Total , 11 



West of this, No. 1 is lost on the dip, whilst No. 2 is cut out as 

 sbown in fig. 5, together with the overlying bed. The consideration 

 of this feature belongs more properly to the fourth block (D). 



* Perhaps the construction of the new arch may have helped this. 



