BLAKE — Olf A NEW PISH-JAW EEOM THE GAULT. 133 
might have been a comparatively shallow lake, caused by the water of 
the melted ice sustained in the hollowed surface of the glen-glaciers. 
The gradual melting of such glaciers would cause a weakening of the 
retaining barriers of the glacier-lake, and sudden debacles might 
occur ; or the streams which now run through the glens may have 
been originally streams issuing at the feet of the glaciers, and cutting 
out the valleys beneath them ; such streams do undermine glaciers, 
and when the collapse of the ice into the cavities or its launch forward 
took place, the lake on the summit might be discharged, or it might 
be merely and placidly slipped down to a lower level without any or 
with oaly a trifling discharge of its waters. 
It might be, moreover, that the melting of the ice of the remains 
of glaciers at a higher level than the surface of this lake, caused a 
continual flow of the water of the lake, and gave it a cutting-power 
in addition to its wave-action. 
At any rate, it seems more possible, as well as more probable, that 
the lake was a glacier- supported accumulation of water, than that a 
great barrier of ice should be erected in front of a body of water to 
shut it back. On the other hand, if the glacier were formed across an 
open plain, where was the water to form the lake to come from ? The 
supposition, therefore, that the lake was formed by the melting of the 
glacier, and was held up on its hollow summit, appears to avoid some 
difficulties to which even the glacier theory of the origin of these 
singular roads is open. 
ON A NEW FISH-JAW YHOM THE GAULT NEAR 
FOLKESTONE. 
By C. Carter Blake, Esq., 
Honorary Secretary to the Anthropological Society of London, and Lecturer on 
Zoology, London Institution. 
My friend Mr. Mackie has handed me an interesting little frag- 
ment of jaw, derived from the Oault at Folkestone. The length of 
the broken fragment of jaw measures 1^ inch ; its absolute breadth 
f of an inch. It contains three teeth, of which the largest is conical, 
incurved, exhibiting around its thickened base a series of sculptured 
linear depressions, parallel with the axis of the tooth, the interior of 
which has been converted into phosphate of lime ; the second and 
the third also exhibiting similar characters, the third especially be- 
ing acuminate, and exhibiting the natural apex of the tooth in an 
uninjured state. The conformation of such a tooth led my friend 
