MODERN VIEWS OE DENUDATION. 
459 
larger ‘valley (sometimes filled to a certain height with marine 
drift) descends on both sides from ridges in a broad sweep, 
flattening towards the middle, at which place it is cut through 
by a channel of varying depth, but generally with steep banks, 
along which flows the stream. It seems to me unquestionable 
that the smaller valley alone is referable to river action ; and, 
as compared with the extent of the wider valley, the amount 
of denudation is often inconsiderable. 
The wonderful freshness of glacial phenomena in this country 
has always appeared to me to offer an obstacle to the accept- 
ance of the views of the modern school, which has not yet 
been fully appreciated, much less answered. The great argu- 
ment with the modern school is time. “ Only grant unlimited 
time,” say they, “ and the work of the gentlest rills, the most 
ordinary frosts and rains, will effect mighty alterations in the 
surface of the earth.” The natural reply is, that the time, 
though vast, is not unlimited, and that the vastness of the 
time is insufficient for the changes. On this point the 
evidence of glaciation is to my mind conclusive, and it may 
be summed up in a few words : — The vast lapse of time since 
the Glacial period in Europe and America has been insufficient 
to effect the atmospheric denudation of the boulder clay, or to 
materially alter the form of glaciated rocks in the valleys, or 
even to obliterate the delicate ice-marks on rock surfaces 
when protected by a few inches of turf or mould. It is un- 
deniable that in many of the old glacial regions, such as 
those of North Wales, the English lakes, the Scottish uplands 
and highlands, the mammilated contour of the hills, 
allowed to be the effect of ice-action of the Glacial period, 
is still maintained with little alteration, and that the very 
valleys themselves, through which the rivers run, are often- 
glaciated down to the water’s edge. In such cases, at any 
rate, no one can assert that the valleys have been formed by- 
the rivers since the glaciers disappeared from off the country 
the actual extent of modern atmospheric and river action 
being generally clearly defined by the scarped sides of the^ 
river-banks breaking the general flow „)r contour of the* 
surface. 
I anticipate the answer to the above reasoning in the? 
assertion that the lapse of time since the Glacial period, is 
really insignificant ; but if any one seriously entertains such 
an opinion (which runs counter to the tendency of recent 
investigation), he must be prepared to produce some evidence 
beyond speculation. The time, at any rate, has been suffi- 
cient to allow of considerable changes in the relative position 
of land and sea, and other physical phenomena requiring 
length of time. Yet the testimony of the rocks is against 
VOL. v. — no. xxi. 2 i 
