242 JOWETT AND MUFF : GLACIATION OF BRADFORD, ETC. 
lip of the Hawkswortli Valley (p. 208). If there was an ice- 
dammed lake in the Hawkswortli Valley at this period, it must 
liave discharged over or through the ice-barrier, since no part 
of the Hawksworth ridge is cut through by an overflow-channel. 
Consequently it is impossible to give the surface level to which 
such a lake might rise, but it may have been sufficiently 
high to liave covered the broad col (705 feet) behind Hope Hillj 
and to have formed a lake confluent with water impounded 
in the Eldwick Valley. Into this lake the Morton Lake would 
discharge. 
It might be expected that at a later period the level of 
the Hawksworth Lake would sink below the level of the col 
behind Hope Hill, and that the Eldwick Lake would discharge 
over the col or round the southern flank of Hope Hill. There 
is, however, no evidence of the passage of such an overflow. 
The Outlets of the Howden Lake. — The Howden Lake, held 
uj) at the head of Howden Beck, about two miles E.S.E. of 
Silsden, discharged over the spur which forms Rivock Edge, 
into the Morton Lake. The overflow channel is a steep-sided 
winding valley with a broad peaty floor. It exhibits very 
clearly a feature which has been mentioned as characteristic 
of the overflow channels, viz., that the bank on the outer curve 
at each bend is distinctly steeper than the bank opposite on 
the inside of the bend. 
It is perhaps worth while pointing out that whilst the 
Rivock overflow channel does not coincide with a line of a fault, 
the spur through which it cuts is crossed by two faults. These 
trend across the spur parallel to and north-east of the overflow 
channel, but there are no valleys through the watershed along 
their courses. 
The surface level of the Howden Lake when it discharged 
through the Rivock overflow channel was a little below 1,100 
feet above CD. At a later period the overflowing waters seem 
to have escaped by a shallow channel at the foot of Rivock 
Edge. This channel, which is partly filled with peat, indicates 
a discharge at about 1,000 feet. No overflow channel was 
noticed at a lower level. 
