LAMPLUGH : GLACIAL SECTIONS. 
393 
but my present knowledge of the action and effects of the differ- 
ent eroding agencies is far too slight to lead me to any safe 
conclusion on the subject. A few suggestions and speculations, 
however, have occurred to me, and may be taken for what they 
are worth, thus : — 
The upper clay-band in section No. 2 has evidently suffered 
severely from erosion, for only a few hundred yards further north 
it has a thickness of 10 feet, whilst here it is in one or two places 
quite cut through. Now where it is continuous, there is a well 
marked difference in colour between the gravel above and that 
below it, and this is the only distinction between them. But 
where the gaps occur and the gravels come together, the red stain 
of the upper gravel diffuses itself into the lower, and it is very 
difficult to say where the one ends and the other begins. And it 
seems very probable to me, that in section No. 1 also, where the 
erosion has been still more severe, this clay -band once existed, 
but has been entirely cut up, and pushed through and into the 
gravels ; so that here we have really two gravels of different 
ages, mixed with the relics of a once-dividing clay-band. This 
view explains many of the peculiarities of the section. 
I could not positively determine in what direction the force 
which wrought these effects had been applied, if indeed the direc- 
tion were definite at all. But as most of the long tapering protru- 
sions point one way — southward — it is probable that the force 
did act with some degree of regularity. It is possible that the 
cliff-line does not cut the beds at a favourable angle, or this might 
be more striking. • The slickenside markings were generally at a 
high angle to the cliff line, or about W. and E. ; whilst the slopes 
of the bottom of the hollows and the general look of the section 
seemed to show that the movement had been from the western or 
landward side. As the ground slopes inland, this would be from 
a lower to a higher level. 
The disturbed masses of Purple Clay seem generally to 
take the form of wedges, thinning in one or more directions. 
