52 REVIEWS—THE OLD GLACIERS OF SWITZERLAND, ETC. 
with those belonging to the great Drift or Glacial epoch: that period 
in the history of the earth’s mutations, which immediately preceded, 
and gradually passaged into, the present or historic age. Broadly 
spread across the entire northern hemisphere, southward to a mean 
latitude (on this continent) of about 40° .N., and again extending 
many degrees northwards from the southern pole, lie vast beds of 
clay, and sand, and gravel, mixed up with and overlaid by heaps of 
travelled stones or boulders; stones that have been brought by 
natural agencies, often across intervening seas and valleys, and over 
mountain ridges, miles and miles away from their original localities. 
Where hard and compact rocks lie underneath this boulder formation, 
or rise up amongst it, their surfaces are almost always found to be 
rounded, or smoothed and polished, and marked likewise in long and 
straight lines with narrow grooves and scratches. If these peculi- 
arities be not always observable on exposed rock surfaces, their 
absence is chiefly due to the disintegrating action of the atmosphere, 
as they necessarily become obliterated, sooner or later, by the effects 
of weathering. 
In Canada the drift formation is largely developed ; and in many 
places the underlying limestone and other rocks exhibit the polished 
surfaces and the long lines of grooving just alluded to. But it is in 
mountainous countries that the phenomena of the drift epoch are por- 
trayed to usin their grandest outlines. There,in many localities within 
the limits of latitude already pointed out, the hill-sides present their 
rounded contours, smoothed, polished, and striated ; the hill-tops bear 
their loads of boulder stones, balanced one upon another, or perched, 
perhaps, on isolated points of rock ; and the valleys show their exca- 
vated hollows and lake-basins, their barriers of heaped up boulders, 
their high and furrowed ‘walls, with other memorials of abrading 
agencies belonging, it may be there, to an older time, but which 
are still in action amongst the frozen solitudes of the remote north, 
and in the higher valleys ofthe Alps and other mountain chains. In 
these vaileys the broad ice-rivers still slowly push their way amidst 
the surrounding rocks, wearing and abrading them, and piling up at 
lower levels their stony burdens in the form of huge moraines.* 
This however leaves the tale half told. To complete our view of the 
phenomena under which the drift accumulations took place, we must 
* In many glaciers the formation ofa terminal moraine is prevented it should be observed 
by the action of the stream which results from the melting of the ice. 
