Oldal 127 [127]
COLOURS IN STILL WATER 69
of the suspended particles in increasing number over¬
powers that due to the water itself. It is hardly
necessary to add that the colour of thick or muddy
water 1s not the colour of the water at all, but of the
solid particles it carries. Thus the Upper Engadine
lakes, the water of which is a fine blue-green,! owe
the brilliancy of their colouring to the unceasing
supply of minute white particles brought down by the
glacier-fed torrents. These lakes, which are four in
number and connected by short lengths of river, pre¬
sent a distinct gradation in colouring from the upper
to the lower. For it is at the head of the valley that
there are the greatest number of affluent streams;
and the uppermost lake, the Silser See, receives there¬
fore more than its proportion of glacier dust. The
water in passing through this lake deposits a great
deal of the dust as sediment, only the finest particles
being carried on to the next lake, so that the propor¬
tion of suspended particles diminishes from lake to
lake. Hence the corresponding gradation in brilliancy
of colouring. In early summer, when the glacier
streams are swollen and turbid, the upper lakes be¬
come almost milky in appearance; but by the time
the river has reached the St. Moritz lake, the last of
the series, it has dropped most of its glacier dust,
retaining just enough to display the full beauty of its
blue-green colour, though it is perhaps surpassed in
brilliancy by the little Campfer lake above. In the
sea similar changes of colour accompany changes in
1 The colour of the water of these lakes is seen to advantage in
the blocks of ice sawn out of them in winter, which will doubtless
be found somewhat greener than the pure blue of a glacier crevasse.