Yol. 6$.~] ORIGIN OF CERTAIN CANON-LIKE VALLEYS. 495 



In another boring 2 miles south-west of Sandy, in Bedfordshire, 

 on low ground near the Greensand-escarpment, Boulder-Clay 104 

 feet thick was found overlying the Oxford Clay, about 100 feet 

 below the level of the Bedfordshire plain and but little above that 

 of the sea. 1 



Such cases seem to indicate pre-Glacial valleys, subsidiary to 

 that of an important river flowing in a north-easterly direction 

 towards the Wash, at a level considerably lower than the River 

 Ouse at present. 



Borings at Boston, Fossdyke, and Long Sutton, farther to the 

 north-east, beyond the limits of the map, in which Boulder-Clay 

 was shown to extend from 100 to 160 feet below sea-level, 2 may 

 represent the seaward extension of such a drainage-system, excavated 

 at a time when England stood higher than it does now. 



Approaching more nearly the Oxford region, we find a boring 

 near Stony Stratford, in the upper part of the Ouse basin, with 112 

 feet of Drift, resting upon the sub-Glacial surface at about 115 feet 

 above Ordnance-datum. 3 The present level of the nearest part of 

 the Oxford plain is 100 feet higher, suggesting that the drainage of 

 the latter may have been originally towards the Fenland through 

 this Drift-filled valley and some channel now hidden by Glacial 

 deposits, which are in that region of considerable thickness. 



At Buckingham, for example, 6± miles south-west of Stony 

 Stratford, a well was carried for nearly 70 feet through Glacial 

 gravels to a level of about 220 feet O.D., without piercing them ; 

 and another boring in the same locality showed 78 feet of 

 Drift. 



Assuming that the borings at Buckingham and Stony Stratford 

 represent portions of the same pre-Glacial valley, it is improbable 

 that the former coincides with its maximum depth near that place, 

 as the longitudinal rivers of the Jurassic plain have no such fall 

 as 100 feet in 6 or 7 miles ; under any circumstances, the valley 

 could hardly have terminated abruptly near Buckingham. 



If, moreover, the Glacial deposits could be removed, it would be 

 found that the Oxford plain was formerly connected with the basin 

 of the Ouse by a valley of a more important character, wider as 

 well as deeper, than that which still exists. 4 Such a valley seems 

 to have no meaning, and its origin is not easy to explain, unless 

 we regard it as excavated by a river flowing from the south-west ; 

 in fact, by the primeval Thames. 



1 Eeported by Mr. J. Hopkinson, Quart. Journ. Geol. Soc. vol. lix (1903) 

 p. 49. The pre-Glacial valleys may have been deeper than the figures given 

 above; it seems improbable that these chance borings should always have 

 coincided with their greatest depth. 



2 ' The Geology of the Borders of the Wash ' Mem. Geol. Surv. 1899, 

 pp. 115-18; see also 'The Water-Supply of Lincolnshire' Mem. Geol. Surv. 

 1904, p. 171. 



3 Eeported by Messrs. Le Grand & Sutcliff. 



4 At Stony Stratford, as we have just seen, the bottom of the pre-Glacial 

 valley was about 100 feet lower than the present level of the River Ouse at 

 the same point. 



Q. J. G. S. No. 252. 2 n 



