Vol. 58.] GLACIER-LAKES IN THE CLEVELAND HILLS. 501 
event of a lake overflowing this way the advantage of even 5 feet 
would be decisive; it is, however, by no means certain that the 
Kirkham-Abbey route had the initial advantage. Mr. Fox-Strang- 
ways is of opinion that it had, and that the Coxwold-Valley 
erosion has no connection with the river-systems of the country, 
and is probably of later date than any of these river-gorges. 
I am unable to accept his explanation, which is, moreover, rendered 
unnecessary, in my judgment, by this consideration, that the Coxwold 
Valley itself was blocked by ice. The great glacier which descended 
the Vale of York obstructed the drainage of the western edge of 
the Cleveland area, and produced upon a small scale phenomena 
similar to those which are displayed in the east and north. It 
extended for more than 10 miles, perhaps much more, down the 
Vale of York below Coxwold, and its terminal moraine at High 
Catton attains an altitude of more than 100 feet. It therefore 
seems reasonable to suppose that at Coxwold the ice rose quite as 
high as the watershed. More than this, the officers of the Geological 
Survey have mapped Boulder-Clay at an altitude of 279 feet in the 
Coxwold-Gilling Valley, which was, I believe, invaded by a lobe 
of the glacier. 
The third point of difference is as to the exact nature of the 
gravel-bench at Hutton Bushel. Mr. Fox-Strangways regards it as 
a lake-beach, but reasons fully stated later have led me to conclude 
that it partakes more of a deltaic nature, and that it came into con- 
tact with the static waters of Lake Pickering only at the western 
extremity. 
Mr. Fox-Strangways has referred in his Memoir to a singular 
abandoned valley entering the Vale of Pickering in the south-west, 
near Settrington. He remarks that the cause of the alteration of the 
drainage is not very clear. I would, however, point out that this 
valley is excavated in the eminently porous and absorbent. Corallian 
rocks, in which deserted valleys abound, as they do in the Chalk-area 
of the Wolds. ‘Two general causes of these deserted valleys may be 
here noted :—(1) the dry valleys of the Chalk Wolds, and certainly 
many of those in the Corallian limestones, were excavated during 
the Glacial Period, when the rocks were in a frozen state, and there- 
fore were impervious to water; and (2) many valleys in the Corallian 
limestones have been abandoned by streams which have found their 
way into subterranean courses, in the manner so common in areas of 
compact limestone. I have visited the spot, and have no suggestion 
to offer; but, so long as the phenomenon is unexplained, it remains 
a possible exception to generalizations respecting the intimacy of 
the association of deserted valleys with evidence of ice-action. 
The evidence adduced by Mr. Fox-Strangways may, I think, be 
regarded as placing Lake Pickering among the well-established 
facts of Glacial geology; and we may proceed to consider one of the 
affluent streams, and see what conclusions may be drawn from its 
features. ‘There are many large valleys opening into the Vale of 
Q.9.G.8. No. 231. 2M 
