of Fossil Bones in a Marl-Pit near North Cliff. 229 



doubt from whence the materials which formed those pits are 

 derived ; and when we reflect upon the low level of this coun- 

 try, not more than ten or twelve feet above the sea at high 

 water, we shall be inclined to regard the present beck, which 

 has of late years been deepened to drain the land, as having 

 been quite adequate to have deposited the marl, to have kept 

 the pond, in which the Planorbes have lived, replenished with 

 water, and to have washed into it the land shells and the 

 bones of the animals which frequented its banks. 



I'he marly deposit itself, then, furnishes no precise indica- 

 tion of the time when these animals lived ; but the gravel and 

 sand which lie over it bear a very different character, and 

 have undoubtedly been placed in that situation by different 

 means. Some persons may conjecture that they have been 

 accumulated there by high tides and ancient inundations of 

 the Humber. I think otherwise, for the following reasons : 



The white flint and chalk gravel of this district not only 

 extends at or near the surface nine miles from hence westward 

 along the foot of the Wolds, as far as Barmby Moor, and is 

 of such a depth as to be worked at several points for gravel, 

 but further to the southward and westward it passes under 

 the great diluvial deposit of the vale of York. At Sutton 

 upon Derwent I find it to lie under sixty-six feet of this de- 

 posit : at that place and at Elvington it contains the supply 

 by which the wells are filled ; and when it is penetrated into, 

 the water rises more than fifty feet, and blows up a great 

 abundance of the angular fragments of white flint. It may be 

 traced along a line drawn from hence to North Cliff, and fol- 

 lows the hills eastward to Hessle on the Humber, where it is 

 seen lying again under the above-mentioned deposit : the beds 

 are perfectly distinct; the one consisting of chalk and chalk- 

 flints, mingled wjth Gryphsa incurva, where it comes near 

 the lias ; the other consisting of the sandstones and blue lime- 

 stone of the west of Yorkshire, mixed with pebbles from the 

 slate rocks, syenite and granite of Cumberland and West- 

 moreland. Where it is in the form of gravel it is locally di- 

 stinguished from the other by the name of the graij gravel ; 

 and where it consists of cobbles of mountain limestone, &c. 

 embedded in clay, it is called by the well-sinkers the black 

 bed. The latter is the bed which lies upon the white gravel 

 at Sutton and at Ilessle. The mighty torrent which has last 

 deluged this great plain has left the relics of the same rocks 

 and fossils in the cliffs of Holderncss as in the gravel hills at 

 York and at Holme. 



Nor was the current wliich hud previously covered the 

 country under the chalk-hills with the fragments of that for- 

 mation, 



