677 
vance, or, to use the words of Agassiz, from which they expand. 
Now whilst in the present days, a small glacier hangs to the sides of 
a mighty giant like Mont Blane, having the altitude of 15,000 feet, 
our Welch hills, having a height only of 4000 feet, had glaciers, by 
the showing of Dr. Buckland, of a length of many miles. Again, in 
the same memoir, which fills so large a portion of the principality 
with glaciers, the author comments upon certain facts already well 
known to us, viz. the existence upon Moel Tryfane and the adja- 
cent Welch mountains of sea shells of existing species, at heights of 
1500 and 1700 feet above the sea, where they are associated with 
mixed detritus of rocks transported from afar, all of which have 
travelled from the North, the hard chalk and flints of the North of 
Ireland being included. How are we to reconcile these facts with 
the theory that the greater part of the country in question was 
frozen up under the atmosphere in some part of the same modern 
period? Unable otherwise to explain how marine shells should be 
found on mountains which are supposed to have been previously 
and during the same great period occupied by terrestrial glaciers 
the accumulation of ages, Dr. Buckland invokes anew the aid of 
the old hypothesis of a great wave. This wave, rolling from the 
north, must have dashed over the mountains to a height of near 
2000 feet, depositing as it went gravel, boulders and fragments, 
derived from places 200 miles distant, and transporting also marine 
shells in its passage. But is it not more natural and accordant with 
all the data upon which our science has been reared, to suppose that 
when such shells were deposited, the parts of the mountains so 
affected were permanently beneath the sea, than to call into play the 
assumption of the passage of so mighty a wave? At one moment 
the argument used is, that scratches and polishings of rock must 
have been done by ice, because in existing nature it has been found 
that ice can produce such effects; and in the same breath we are told 
that beds of shells have been placed on a mountain by an agency 
which is truly supernatural. 
In fact, the “glacier” theory, as extended by its author in proving 
too much, may be said to destroy itself. Let it be limited to such 
effects as are fairly deducible from the Alpine phenomena so clearly 
described by Agassiz, and we must all admire in it a vera causa of 
exceeding interest; but once pass the bounds of legitimate induc- 
tion from that vera causa, and try to force the many and highly 
diversified superficial phenomena of the surface of the globe, into 
direct agreement with evidences of the action of ice under the 
atmosphere, and you will be driven forward, like the ingenious 
author of the theory, so to apply it to vast tracts of the globe, as in 
the end to conduct you to the belief, that not only both Northern 
and Southern hemispheres, but even qguast tropical regions, were 
shut up during a long period in an icy mantle. Once grant to 
Agassiz that his deepest valleys of Switzerland, such as the enormous 
chasm of the lake of Geneva, were formerly filled with solid snow 
and ice, and I see no stopping-place. From that hypothesis you 
may proceed to fill the Baltic and Northern Seas, cover Southern 
