XXXVl PEOCEEDIXGS OF THE 



beds must rest, may be inferred, but it is equally clear tbat the 

 Mesozoic column becomes thinner as we advance northwards from 

 London, as shown by the boring at Ware which reached Silurian 

 rocks at a depth of 800 feet.* It is also equally certain that the 

 Jurassic rocks are absent altogether beneath Ware and London. 

 We cannot therefore expect that these various beds seen to-day, 

 including the clays on which they rest, have any great extension 

 within the Chalk area, beneath which we see them dipping. 

 Somewhere between here and London they are sure to knock up 

 against the old rocks, and when we remember the oscillations that 

 have taken place at various epochs, it is not difficult to believe 

 that, duiing the Portland period, either a shore-line or a line of 

 rocky shallows was not far oif in a south-easterly direction. At 

 present the thickness of the Secondary rocks here may be about 

 1,000 feet; they are 800 feet thick at Ware, thirty miles to the 

 east, and 1,200 feet thick at Burford, thirty-six miles to the west. 

 The boring at the Asylum, near Stone, close by, went through 

 570 feet of beds, and terminated somewhere in the Oolitic formation. 

 For a long period, in the interval which preceded the deposition 

 of the Chalk, this region underwent considerable vicissitudes, 

 accompanied by much denudation. Then came a time when the 

 whole region, far and wide, sank, and the Cretaceous sea flowed 

 over everything for ages. The story of the uprise of its deposits 

 and of their sculpture, whereby the great escarpment of the 

 Chilterns was produced, belongs to another chapter iu the chequered 

 history of the earth." f 



A vote of thanks was then accorded to Mr. Hudleston, and the 

 members of the two societies walked back to Aylesbuiy, and after 

 having tea there, left by train for theii- respective destinations. 



Field Meeting, 12th June, 1880. 

 ASHRIDGE. 



A large number of members assembled at Tring Station, and 

 walked, some by Aldbury and others by a more circuitous route, to 

 the hill on which the Bridgewater Monument stands. Before 

 ascending the hill a search was made for orchids, but, owing prob- 

 ably to the very wet weather at the time of flowering the year 

 before, few were seen. Epijmctis latifolia, the broad-leaved helle- 

 borine, and Ophrys Apifera, the bee-orchis, were however detected, 

 and also the deadly nightshade, Atropa Belladonna. 



Near the Monument, on sloping ground commanding a fine view 

 of the country to the north, a halt was made, and here, sitting in 

 groups under the pleasant shade of wide-spreading beech trees, the 



* See ' Trans. Watford Nat. Hist. Soc.,' Vol. II, p. 245. 

 t ' Proc. Geol. Assoc.,' vol. vi, p. 352. 



