JOT 
-coming by way of the Silsden Pass, thus isolating the 
high ground to the east ? An ice-sheet in Wharfedale thick 
enough to leave striae at an elevation of 900 feet, as it is said* 
to have done, must have shed an offshoot through the gap in 
the intervening ridge between Addingham and Silsden. For 
this to be of any service, we must assume that Rombald's 
Moor was a separate gathering ground ; a proposition which 
probably no glacialist is prepared to accept. Yet the area 
west of Hope Hill, and the hills below the Eldwick reservoir, 
present a strikingly moiitonnee outline, which recalls at once 
the moulding power of a sheet of ice. The case in point is 
analagous to certain phenomena in the Eden valley ; for the 
explanation of which Mr. Gfoodchild,t following Prof Eamsay, 
suggests that there were various currents at different levels 
in any given ice-sheefc over the same ground. 
The Airedale glacier cannot well have exceeded 300 feet 
in thickness, for, while nearly filling, it did* not overflow the 
Bradford basin. If we suppose that Rombald's Moor, 1,300 
feet high, shed a stream of ice over the western shoulder of 
Hope Hill ; such ice-stream — the Aire valley ice being 300 
feet in thickness — might over-ride the latter, and so flow to 
the east of the Bradford watershed. 
But whatever theories we propound, the subject of our 
inquiry is beset by difficulties, and it is only by patiently 
observing and noting all the facts, that we may hope to dis- 
cover a satisfactory solution of these perplexing problems. 
* Since the above -was read, quarrymen have exposed a grit surface well 
polished and ice-scratched, the strife running due west and east, along the 
northern edge of Rombald's Moor, 900 feet aboye the sea. 
+ Quar. Jour. Geol. Soc. XXXI. 68. 
