Vol. 58. | GLACIER-LAKES IN THE CLEVELAND HILLS. 481 
down during the persistence of the ice-barrier; and when this 
happens, we find the events recorded in the form of a river-gorge of 
a breadth disproportionately small as compared with the magnitude 
of the stream, and an abandoned valley of a normal form obstructed 
near the deviation by the moraine. 
Such a gorge is that of the River Nidd near Knaresborough, de- 
scribed by me ina paper presented to the British Association in 1896, ' 
In other cases, it may happen that upon the retreat of the obstructing 
ice the drainage may be resumed upon the original lines, though 
perhaps over a raised floor of Drift. When this is the case, the 
temporary overflow-channel will be abandoned, and will thereafter 
carry only such small amount of drainage as belongs to its own 
very limited catchment, sometimes even none at all. 
Here now are two distinct types of anomaly in valleys both 
bearing the canon-like aspect that tells of rapid erosion: but in one 
case the valley is narrow out of proportion to the stream that 
occupies it; in the other the stream, if stream there be, is 
disproportionately small for the valley. In every district in which 
I have found these evidences, both types occur; often, where a 
chain of parallel lakes existed draining one into another, the two 
types of valleys occur in rough alternation, as in the country between 
the Ure and the Wharfe from Hackfall to Tadcaster. 
The anomalous valleys which at present constitute the main 
drainage-channels of Cleveland, present no special features to which 
I need deyote attention here. Their recognition is easy, and their 
characters simple; but the deserted channels, having remained 
practically unchanged from the time of the departure of the ice, 
with all their characteristics unimpaired, are of singular interest 
and demand careful consideration. They appeal to me as perhaps 
the most impressive memorials of the Ice-Age that our country 
contains. : | 
LV. GENERAL CHARACTER OF THE ABANDONED CHANNELS. 
These valleys conform to four principal types in regard to 
position. | 
(1) Direct overflows.—Those which trench the main water- 
shed of a country so that the overflow is directly away from the 
ice—these may for convenience of reference be termed direct 
overflows. ‘The finest example in the Cleveland area is Newton 
Dale. Direct overflows are usually found to trench only the lowest 
cols of a given watershed, except where the obstructing ice has 
approached very near to the watershed. They generally occur 
singly, one overflow serving for the drainage of a considerable area 
of the iceward side of the country; but when the watershed is 
very uniform in height, and the ice has at one stage actually sur- 
mounted it, then several parallel overflows may be developed out 
of the gutters which are trenched in the outer slope by water 
1 Rep, Brit, Assoc. 1896 (Liverpool) p, 802, 
