394 
LAMPLUGH: GLACIAL SECTIONS. 
These wedges, detached from the main mass, appear in some 
cases to have been pushed over gravels, upturning their edges 
or entirely contorting and smashing them ; in others, to have 
been forced forward through them, so as to cut cleanly without 
destroying them ; whilst sometimes the clay seems to have been 
squeezed or injected, since the bedding of the gravel curves round 
the intruder. ( enlarged section 3 for example )< 
In many cases I think the gravels must have been frozen 
hard to allow of so clean a cut ; as in the hollow to the left of D, 
section 1, where the gravel and sand are bedded straight against 
a vertical wall of boulder clay, with no other disturbance than a 
single layer of vertical pebbles half fixed in the clay and slightly 
dragged with it : yet both the sides and bottom of this hollow 
showed scoring. In some cases it seems to have been masses of 
frozen gravel that have ploughed into the clay ; in others the clay 
is certainly the intruder. Other evidence of the once frozen state 
of the gravels is afforded by the somewhat common case in which 
a thin sheet of gravel stands vertical between beds more or less 
horizontal, sometimes — as in the enlarged section 3 — with a thin 
and interrupted film of clay forming one border. In these cases 
the gravel may have been frozen hard to its clayey bed, so that 
when torn up, it has sometimes dragged a plate of its resting 
place with it, and has then been tilted and jammed upright, with 
the clay still adhering to it. In the case of the wedge-shaped 
masses of clay before mentioned, I think the clay-band may 
have been broken into huge cubes, and these forced forward till 
firmly fixed amongst the frozen gravels, and the top may have 
afterwards been squeezed out or dragged for a little distance 
further. In some cases a slight movement seems to have taken 
place during-, or after, the deposition of the marls, slightly affect- 
ing them ; as in one or two places the line between the marls and 
gravel stands at an angle steeper than I think the marl could be 
deposited on.* 
* This is more evident now than when the section was made. 
