410 Dr. A. Irving—BSections of Bagshot Beds. 
Swinley (e.g.), where its horizon is determined by its relation to 
the Upper Bagshot Sands of Tower Hill, and to the dark green 
sand which is found everywhere beneath it in the trial holes which 
have been made in Mr. Lawrence’s brickyards, it attains a thickness 
of 12 to 14 feet.1 The increased argillaceous character of the green- 
earth beds in the Wick Hill section, to such an extent as to almost 
obliterate their green earthy character, by the development of strong 
clays, is definitely anticipated in the intermediate country in the 
direction of Wellington College. 
Thus a strong unctuous grey clay is found in thin beds inter- 
calated with the green earths on the north side of Wellington 
College estate; and in what is known as Holloway’s Land on the 
north side of the Duke’s Ride, the clays of the green-earth series 
are so considerably developed, that a few years ago they were 
worked for bricks. They are partly grey, partly purplish clays, 
with numerous included patches and small layers of the typical 
green earthy sands. The upper clay-bed in the Wick Hill section 
has more green earthy sand in proportion to the clay-seams than it 
has in the cutting north of the station; but both the green sand 
and the clay-seams are of the same quality, and the physical 
character of the bed is the same in both sections. More extended 
observation of the Bagshots has led me to regard the upper 5 feet 
or so of coarse loose sand, with a few strongly-marked clay-seams 
in the California sub-section, as not a true Bagshot Bed at all. It 
is much less compacted than they are; it has a strong pseudo-dip to 
the north, as is seen again in the excavation by the rifle-butts ; 
and in one pit-face I measured lately a dip of 23° W.N.W. It is, 
I believe, nothing more than a deposit formed by the run of the 
hill to the south in post-Bagshot times.? The section-diagram and 
the marginal descriptions of the several beds are made from 
measurements and notes taken on the afternoon of the day on which 
the clean excavation was made for me in 1886, and from the 
open clay-pits in the brickyard. The lower part of the California 
sub-section is constructed from data furnished in two wells at the 
engine-house. 
There being good vertical sections at right angles of the lower 
clay-and-laminated-sand-bed in the open pits in the brickfield, the 
absence of any measurable dip in it may be predicated with some 
degree of certainty. Yet a considerable dip would be required in 
order to bring them into the Lower Bagshot, if we take into account 
the position of the green earth series (20 feet exposed) with the 
clay-bed above it at Heath Pool, the position of the Upper Bagshot 
' For fuller details see Section L of my paper on ‘‘ The Stratigraphy of the Bagshot 
Beds of the London Basin,” Q.J.G.S. May, 1888. 
* A similar ‘run of the hill,’ with a pseudo-dip ‘rather north of east’ on the side 
of Thorn Hill, Aldershot, has been wrongly noted as a dip of the Bagshot beds 
there (Q.J.G.S. vol. xlii. p. 410). Here, however, the character of the deposit is 
more suggestive of rearrangement in a shallow lake; possibly on the margin of the 
Thames-valley arm of the great extra-morainic lake of the late Prof. H. Carvill 
Lewis, whose loss we deplore. To add anything to the sketch of his character at 
the end of the article in ‘‘ Nature” (August 9th, 1888) would be an attempt to ‘ gild 
refined gold.’ 
