312 
KENDALL : THE GLACIATION OF YORKSHIRE. 
while I am not, in view of Hoist's observations upon the glaciers of 
Greenland, prepared to endorse this view I still recognise that the 
improbability of such a material being laid down in front of a glacier 
is very great, and therefore I am impelled to regard boulder clay as a 
sub-glacial deposit. If this be so then it will follow that the ice of 
the great glacier overrode both the moraine at York and that at 
Escrick, plastering their inner and outer faces with clayey ground- 
moraine. However we interpret the maps — admitting the pre- 
mise that boulder clay is not laid down upon terminal moraines 
outside the edge of the ice — the conclusion must follow that these 
two moraines were over-ridden. If the median strip of sand and 
gravel were the crest of a ridge against which the boulder clay was, 
as I have suggested, banked, then the ice must have passed over this 
ridge to lay down the clay on the outer face of the moraine. If, on 
the other hand, we were to regard the sands and gravels as superposed 
upon the boulder clay, then we should be compelled to regard the 
great rampart of boulder clay upon which they rested as a terminal 
moraine which had been completely mantled by ground moraine, and 
subsequently capped upon a retreat of the ice by a second gravelly 
moraine. Which of these views is the correct one I am not in a 
position to say, but my impression is that the former better accords 
with the facts, as I have seen several sections in which boulder clay 
rested on the gravels, and one was quite on the summit of the 
moraine at " The Mount," York." 
I am well aware that objection will be taken to my explanation 
on the grounds of the inherent improbability of a glacier over-riding 
a moraine without levelling and redistributing it, and adverse nega- 
tive evidence may be produced from the Alps and Norway ; but I 
submit that there is no parity between the small torrentiform glaciers 
of the Alps and such a mighty ice-river as laid down the York 
moraine. A comparison would be more appropriate with the great 
Muir glacier of Alaska (though even there the gradient from the 
snowfields was immensely greater than that of the case we are con- 
sidering), and here we find that the ice has actually passed over 
* I would, however, remark that this material was much more stony and 
sandy than the generality of boulder-clays, and much more like ordinary 
mora:n>stuff. 
