ttom or underflow, which is always an attendant
of a glacier.

The glacier continues its flow down the mountain side till in some cases
it reaches quite to the valley below, and in others it stops short, as
the action of the sun is so great that it melts entirely away at this
point as fast as it moves down. In the winter time, however, the glacier
may flow far down into the valley and will accumulate greatly in bulk,
owing to the fact that the ice forms from the precipitation of snow on
top faster than it melts away underneath. If it were not for the fact
that in summer the glaciers melt faster than they form, the whole valley
would in time become a great river of ice. It is the case in Switzerland
that some years the accumulation is greater from snowfall than
diminution from melting. If this condition should continue it would
become a serious matter.

In the downward flow of a glacier--slow as it is--there is an exhibition
of wonderful power; great bowlders are torn from their beds and either
ground to powder or carried down to the end of the glacier, to be
dropped with the other debris that has been carried there by the same
force, forming an accumulation that geologists call the "moraine." Of
these moraines we will speak more fully later on.

It was the privilege of the writer some years since to visit the great
glaciers of Switzerland and to some extent study their action. Some
rivers have their origin chiefly in melting glaciers. They start as ice
rivers and end in rivers of water. The effects during the great ice age
of some of these glacial rivers, which are now extinct, are very
remarkable; we shall have occasion to refer to them when we come to
treat of the glacial period.

There is a glacial river flowing which is fed largely by the great Rhone
glacier in Switzerland. The water from this river is almost as white as
milk, which is occasioned by the grinding action of the great ice blocks
on the rock as it flows down the sides of the mountain. These glacial
rivers are much higher in summer, of course, than in winter, some of
them having not only an annual fluctuation, but a diurnal one. The
former is caused by the cold of winter, and the latter because it
freezes to some extent at night and checks the flow of water. The
difference between day and night in these high altitudes is very marked.
While it is extremely hot in the sun, it is cool the moment we step into
the shade.

I remember walking across one o