16 
The Glacial Ori(j'in of Cliffs — Davis. 
When the rapid weiithering of a soft bed, S, fig. 8, uudermme* 
the outcrop of a hard bed, H, the fragments from the cliff-face 
of the latter fall down the slope and form a protective covering 
or talus which retards the further wasting away of the soft bed 
beneath it. An approximate adjustment of form will be at- 
tained when the supply of stony blocks from the cliff about 
equals the loss by weathering from the talus. If the supply 
be for a time faster than the waste, the outline, a a, will change 
to b b, or to cc, until the supply is reduced by the gentler slope 
and smaller face of the weathered and partly buried cliff and 
comes to equal the loss from the talus, which has been in- 
creased by reason of the greater surface exposed to weathering. 
This adjustment undoubtedly prevails in the non-glaciated part 
of the country. Complete adjustment however is not reached. 
The loss must be always a little in excess, for the mass as a 
whole is slowly wasting away. As the waste progresses, the 
cliff that was steep and bold in the youth of the region, falls 
back and weakens in its middle life and fades away in its old 
age. 
Although the' conditions that determine whether b b or c c 
will be the form selected by the balance of natural processes, 
during early maturity , the occurrence of a strong transporting 
agent at the foot of the slope may be named first. A sea-shore 
cliff has little talus; the waves carry the cliff-waste away as fast 
about as it falls. A river may locally be as effective but these 
agents do not enter our problem, unless perhaps in the case of 
the Palisades, and even there the Hudson is so quiet as to ext-rt 
little control. Climate is also an important condition in de- 
termining the form and size assumed by the talus. In a wet 
