Prof. Sivinnerton — •Dreikanter Periods in S. Notts. 209 



doubt future expluratiou will reveal their presence beyond these 

 limits. They are most abundant in the soil of a sheet of gravelly 

 drift which at Bestwood lies near the 400 ft. contour, but drops 

 gradually towards the soutli and south-east. Similar gravels at 

 Clifton and Wilford lie just above the 200 ft. contour. In any 

 ploughed field situated on this sheet one may reasonabh' expect to 

 collect a basketful of ' dreikanter' in the course of a short search. 



The pebbles which have been worn are derived for the most part 

 from the Bunter conglomerate, but the question naturally arises as to 

 when they became wind-worn. In this connexion several periods 

 suggest themselves, viz. Triassic times, late Pleistocene times, and 

 ([uite recent times. 



There seems to be no doubt that the prevailing climatic conditions 

 in Britain during the Triassic period were such as to favour wand 

 action, but of course locally these conditions were counteracted bv 

 others. Immediately around Nottingham, for example, the Bunter 

 conglomerate exhibits all the characteristics of a rapidly formed 

 deltaic deposit. It is not surprising, therefore, that though this 

 formation has been subjected to assiduous search it has not yet 

 yielded indubitable wind-worn stones. After deposition had ceased, 

 however, its surface seems to have been vigoroush' swept by winds. 



20F1 



IQOfr 



200 (-r 



Section made from a i^ortion of the sewer trench opened along Arnot Hill Koad. 

 Dotted area, Bunter Conglomerate. Black area, ' dreikanter '-bearing 

 gravels. Lined area, plastic clay at the base of the Keuper Waterstones. 

 Other areas, soil, subsoil, and alluvium. 



This is indicated by observations made during the opening of a sewer 

 trench along Hallam's Lane (now Arnot Hill Road), which leads 

 from Arnold to Arnot Hill. My attention was called to the trench by 

 Mr. R. E. Clarke, the surveyor for the Arnold District Council, who 

 had been struck by the peculiar subsoils which were being entered. 



The trench ran slightly obliquely to the strike of the Keuper, and 

 for 70 yards its floor lay in the substance or on the surface of the 

 Bunter, whilst its sides were made up of the bottom beds of the 

 Keuper Waterstones (PI. XVI, Fig. 1). The lowest of these was 

 a plastic clay, 3 feet thick and of deep-red colour, in its unweathered 

 portions. The surface of the Bunter conglomerate npon which it 

 rested can only be described as wind-swept (PI. XVI, Pig. 2), for 

 many pebbles projected more or less completely above the surface, 

 others rested loosely upon it, and all, in striking contrast to the 

 typically water-worn form of those still embedded in the conglomerate, 

 showed clear signs of wind erosion. 



DECIDE VI. — VOL. I.— NO. V. 



14 



