604 A. J. JUKES-BROWNE ON" THE RELATIVE AGES OE 



Beck. Its diversion into the Steeping valley may have been effected 

 in exactly the same way as that of the Tetford brook. 



Before the diversion of the- Tetford brook the extreme sources of 

 the Steeping river would be at Salmonby ; and before the diversion 

 of the last-mentioned brook, the sources of the Steeping were pro- 

 bably near Stainsby ; and at some still earlier period, all the streams 

 draining the country north of the ridge on which Hagworthingham 

 stands, ran north-eastward into the Calceby valley. 



The mapping of the district by myself and Mr. Strahan, leads us 

 to conclude that before the oldest Boulder-clay was laid down, the 

 chalk escarpment occupied a more westerly position, and the line of 

 the Steeping valley was occupied by the broad outcrop of the Middle 

 jNeoconiian clay, with valleys opening south-westwards and drained 

 by brooks running in that direction. On this surface the so-called 

 Chalky Boulder-clay was deposited, and was probably banked up 

 to the then edge of the Wold escarpment, as is the case further 

 north. When detritive agencies began to operate on this district 

 the rain which ran southwards would find a line of weakness 

 along the junction of the Boulder-clay with the Wold scarp. A 

 valley opening southward, or south-eastward, would in process of 

 time be excavated along this line, just as the upper valley of the 

 Bain has been formed under similar conditions. Its bottom for a 

 considerable distance would be formed by the Middle jSTeocomian 

 clay, and it would be some time before the Lower rTeocomian sand- 

 stone would be bared to any great extent above the position of 

 Partney. It is not unlikely that the beck coming down from Lang- 

 ton and Sutterby, and joining the Steeping at Partney, may indicate 

 the course of this line of drainage. The Skendleby Beck was clearly 

 also in existence at this time, and the united streams would doubt- 

 less flow south-east to the coast-line wherever that was. 



As, however, the work of pluvial detrition went on, and a, larger 

 and larger area of the Lower Sandstone became exposed, a great 

 proportion of the rainfall would be absorbed by the sandstone, and 

 thrown out from its base in the form of springs. This would 

 necessarily introduce a new element among the agencies of erosion, 

 and the combined action of rain and springs would cause the valley ' 

 to be extended in a north-westerly direction along the strike of the 

 sandstone, far more rapidly than in any other direction. 



Under these circumstances there is nothing improbable in the 

 hypothesis that the whole of the present valley from Partney to 

 Salmonby has been excavated in Postglacial times, and that, being 

 cut back along a lower base-line, the Steeping river has gradually 

 intercepted the drainage of a district which was once a part of the 

 Calceby-beck system. 



This therefore appears to be a case in which the extension of a 

 longitudinal valley has intercepted and diverted the course of certain 

 streams which originally flowed into a transverse valley, and has 

 entirely altered the drainage-system of a considerable district. 



The conclusions to which I have been led by a prolonged study 

 oi this part of Lincolnshire are opposed to those of Mr. S. Y. Wood 



