o be always recognized, even when they are no longer adjacent to a
glacier nor immediately surround its lower extremities. I may remark
that lateral and terminal moraines alone enable us to recognize with
certainty the limits of glacial extension, because they can be easily
distinguished from the dikes and irregularly distributed stones carried
down by the Alpine torrents, The lateral moraines deposited upon the
sides of valleys are rarely affected by the larger torrents, but they
are, however, often cut by the small streams which fall down the side of
a mountain, and which, by interfering with their continuity, make them
so much more difficult to recognize.

"2. The Perched Bowlders.--It often happens that glaciers encounter
projecting points of rock, the sides of which become rounded, and around
which funnel-like cavities are formed with more or less profundity. When
glaciers diminish and retire, the blocks which have fallen into these
funnels often remain perched upon the top of the projecting rocky point
within it, in such a state of equilibrium that any idea of a current of
water as the cause of their transportation is completely inadmissible
on account of their position. When such points of rock project above
the surface of the glacier or appear as a more considerable islet in
the midst of its mass (such as is the case in the Jardin of the Mer de
Glace, above Montavert), such projections become surrounded on all
sides by stones which ultimately form a sort of crown around the summit
whenever the glaciers decrease or retire completely. Water currents
never produce anything like this; but, on the contrary, whenever a
stream breaks itself against a projecting rock, the stones which it
carries down are turned aside and form a more or less regular trail.
Never, under such circumstances, can the stones remain either at the
top or at the sides of the rock, for, if such a thing were possible,
the rapidity of the current would be accelerated by the increased
resistance, and the moving bowlders would be carried beyond the
obstruction before they were finally deposited.

"3. The polished and striated rocks, such as have been described in
Chapter XIV., afford yet further evidence of the presence of a glacier;
for, as has been said already, neither a current nor the action of waves
upon an extensive beach produces such effects. The general direction of
the channels and furrows indicates the direction of the general movement
o