ki:m»all: thk (;la(mi:k lakks of clkvklam) 
37 
a niik'. Its upper edge, wliere it rests upon the slope of the hills, 
falls f?oin 245 feet on the south of Forge Valley to a little 
over 2(M) feet at VVykeliani. Four deep valleys come down to 
this gravel l)ench, and each of them on reaching it undergoes 
a sharp westerly deflection. Moreover, across the flat top of 
the gravel teriace. a series of deep channels has been left, forming 
an almost complete series of links connecting each valley with 
its iiei^hboui on the west. At the western end. by VVykeham 
and Rushton. the terrace is extremely uneven, and it comes to 
an abru[)t and singular termination in a great liorn. running 
for nearly a mile out into the valley, forming a bold ridge on 
which Wykeham Abbey is situated. Shell fragments are common 
in these gravels and they contain many erratics, including Cheviot 
andesites. jaspei- j)ebbles. Magnesian Limestone, gneiss, and 
granite. 
T\w jKMsistent westerly " aberration " of the debouchure 
of tlie \-allevs points to the ()])eration of some constraining agent 
which is no longer ])resent : and when the deserted high-level 
channels which linked these valleys together are reviewed, and 
found to indicate a similar j^ersistent tendency, the constrain- 
ing agent seems to be clearly indicated — ice in the form of a 
glaciei-lo))e would [iroduce this effect. I'pon this hypothesis, 
the edge of the great ice-sheet passed farther inland, where it 
encountered the feeble opposition of the range of heights to the 
south of Scarborough, tlian it could to tlie northward, where it 
was op])osed by a boldei- country, and so was enabled to thrust 
its way U]j the Vale of Pickering to. and a little bevond, Wykeham. 
The phase of maximum extension is. on this view, indicated 
approximately by the gravel-i)atch on Gallows Hill. After 
a very brief sojourn at this extreme extension, a protracted halt 
took place about Wykeham. and the great gravel-mass there 
appears to be the terminal moraine of this ice-lobe. 
Under the conditions now set up. we may suj)])ose the 
Forge Valley overflow to have come into operation, and a vast 
quantity of water from the extensive area of land and ice to have 
come down the incipient channel. This stream would bring 
over a few erratics, along with immense quantities of gravel and 
stones obtained from the denudation of the gorge ; and these 
