BLAKE — ON A NEW FISH-JAW EROM 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 only 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 w r ave-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 FROM THE GAULT NEAR 

 FOLKESTONE. 



By C. Carter Blake, Esq., 



Ilonorary Secretary to the Anthropological Society of London, and Lecturer on 

 Zoology, London Institution. 



My friend Mr. Maekie has handed me an interesting little frag- 

 ment of jaw, derived from the Q-ault at Folkestone. The length of 

 the broken fragment of jaw measures 1]. inch; its absolute breadth 

 | of an inch. Il 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 



