ALLUVIAL COVERING. 17 



and where the discliarge is copious, the sand must needs be washed 

 away, and the gravel alone remain. Some of the sand in the cliffs 

 near Whitby is magnetic, particularly a brown sand found at Upgang. 

 • 4. A brotvn, coarse clay. This clay has an earthy aspect, and 

 is not very tenacious, being frequently mixed with sand and marl. 

 It contains numerous pebbles, nodules, and fragments of stone of all 

 descriptions. This bed forms a large portion of the alluvial cliffs, 

 hieing often several yards in thickness. It is frequently met with 

 immediately below the vegetable soil; the marl, and the sand and 

 gravel, in such places, being either blended with it, imbedded in it, 

 or altogether lost. Sand beds often occur in this clay at a great 

 depth below the surface; as may be seen between Whitby and 

 Sandsend, where a large bed of sand and gravel is found about half- 

 way down the cliff. 



5. A darker, ash-coloured clay ; commonly more compact than 

 the brown clay, and less mixed with marl or sand ; though contain- 

 ing the same abundance of nodules and fragments of stone. This 

 bed, like the former, is often of vast thickness. Sand beds some- 

 times alternate with this clay, as well as with the brown clay. A 

 bed of bfi'own sand is found at Upgang at the very base of the cliffs. 



These two kinds of clay frequently pass into one another, and at 

 the place of their junction are found clouded and intermixed, instead 

 of presenting a distinct line of separation. 



6. A blueish, or blackish, tenacious clay. This bed, which is 

 also in some places of considerable thickness, forms the lowest visi- 

 ble portion of the cliffs, in several parts of Holderness, and in other 

 alluvial cliffs along the coast. It occurs at the bottom of the cliff 

 between Upgang and Sandsend; where its slippery, treacherous sur- 

 face, laid bare by the washing away of the upper beds, and moist- 

 ened by every returning tide, often makes the unwary passenger fall 

 flat upon the beach. 



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