606 A. J. JUKES-BROWNE ON THE RELATIVE AGES OE 



valley be admitted, the absence of the Hessle beds is apparently an 

 inexplicable fact; for, whether these beds have been accumulated 

 under aqueous or terrestrial conditions, it is equally surprising that 

 no trace of them should occur in this valley (if it was then in 

 existence) when they extend so far up the adjoining Calceby 

 valley. 



"What therefore is such a puzzle on Mr. S. Y. Wood's hypothesis, 

 is but a necessay consequence of my postulate that the longitudinal 

 valley is of later date than the transverse valley. I may therefore 

 reasonably regard the position of the Hessle Clay in the Steeping 

 valley as a confirmation of my belief that the whole of thar. valley 

 above Partney has been excavated in Postglacial times, i. e. since 

 the formation of the Hessle Clay, which I regard as the uppermost 

 member of the Glacial series. 



Trent and Witham Y alleys. 



Modern Course of the Trent. — This river is formed by the union of 

 several streams, of which the most important are the Trent, the Dove, 

 and the Derwent, flowing from the north-west off the Derbyshire 

 and North Staffordshire watershed, the Tame and the Soar flowing 

 from the south through the counties of Warwick and Leicester. 

 These streams converge towards a point about ten miles S.S.E. of 

 Derby, their united waters being known as the river Trent, which 

 flows onward in a north-easterly direction through a well-marked 

 valley as far as Newark. 



Here, however, the river bends to the northward, keeping to the 

 west side of the low Rhsetic escarpment, as if it had not been able 

 to cross that comparatively slight obstruction. This northerly course 

 it maintains till it reaches the estuary of the Humber. 



Now the course of the Trent as far as Newark favours the 

 supposition* that it was determined by the westerly slope of a 

 plane of marine denudation across the edges of the Lower Jurassic 

 strata ; but if so, and if it had ever flowed over a surface of Oolitic 

 rocks, why did it not continue this course so as to run in a 

 transverse valley through the Oolitic escarpment and into the 

 Wash instead of into the Humber ? 



It is a significant fact that if the general course of the Trent, south- 

 west of Newark, be prolonged to the N.E., it points to the great 

 gap in the Oolitic escarpment at Lincoln, through which the river 

 Witham now flows. If this transverse gap or gorge be considered 

 only in relation to the small river which runs through it, the 

 manner of its origin is altogether inexplicable ; but if good grounds 

 can be shown for supposing that the river Trent formerly passed 

 through it, the existence of such a gap is satisfactorily accounted for. 



Moreover the anomaly in the present course of the Trent is 

 likewise explained, if it can be shown that the northerly bend of 

 that river is a subsequent diversion and not its original course. 



* Kamsay, Phys. Geogr. and Geol. of Gt. Britain, ed. v. p. 518. 



