440 



ME, H. G. LYONS ON THE LONDON CLAY 



Long Valley by the Farnborough and Farnham Eoad. In this 

 section we get the high ground at the south instead of the north 

 end of the section, which is more convenient for our present purpose. 



On the tops of the ridges north of the Red Church, near the 

 Permanent Barracks, the pebble-bed occurs at the top of the Middle 

 Bagshot ; and a scarped face of one of these ridges nearest to the 

 Bed Church shows a section of the base of the green clayey sands 

 and the top of the clay-beds which form the base of the Middle 

 series. Here, when freshly cut, a dip of about 2 J° north was shown. 

 Going south, Lower-Bagshot sands were shown in a small excavation 

 by the Queen's Pavilion, and again in a sand-pit behind the Lock 

 Hospital, where there are about 20 feet of brown and buff false- 

 bedded sands, and seams of pipe-clay are seen, having a dip of 2-±-° 

 north. 



Further on, at Windy Gap, on Hungry Hill, the same sands are 

 seen, while the London Clay is dug in a small brickyard at the foot 

 of the hill to the east. 



Hungry Hill itself is capped by a considerable thickness of gravel, 

 and below it small springs are thrown out in wet weather, I 

 think by part of the clay-beds which form the base of the Middle 

 Bagshot. 



Quite lately, a well 62 feet deep has been sunk at the Inn on the 

 Farnham Boad by Hungry Hill, and reached clay having all the 

 characters of the top of the London Clay, having passed through 

 buff and brown loamy and sandy beds. There are 4 feet of water 

 in it. 



In extending the drains above the Reservoirs in Bourley Bottom, 

 a bed of green clayey sand was cut into, overlain by a brown 

 loamy clay. This green bed is the one which furnishes all the 

 springs which fill the Reservoirs, and is, I think, the middle bed of the 

 Middle Bagshots, which supplies nearly all the wells in and about 

 Aldershot. The point where it was exposed was between 560 and 

 570 feet above O.D., under Caesar's Camp and Bricksbury Hill. 



The sand is dark green when first dug out, but becomes light on 

 exposure to the atmosphere. 



Prom these considerations I think that the London Clay and 

 Bagshot beds at Aldershot have a constant northerly dip, and that 

 the Bagshot beds lie conformably on the older beds, which have at 

 this point an average thickness of 335 feet. 



In conclusion I will briefly recapitulate the points I have drawn 

 attention to in this paper, and their bearing on the stratigraphy of 

 the district. 



Commencing with the London Clay, I have shown that wherever 

 we can fix the top or base of this formation, we get a dip to the 

 north of from 2^° to 3°; and that this dip, if we restore the portions 

 which have been removed by subaerial erosion, gives us a fairly 

 constant thickness of from 330 to 340 feet. In the table below are 

 given the thicknesses of the London Clay at several places in and 

 near Aldershot ; and wherever I have restored what has been eroded 

 away, I have shown it in this table. The authorities for each 

 section are also given. 



