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COLOURS IN STILL WATER 69 of the suspended particles in increasing number overpowers 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, present 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 therefore 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 proportion 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 become 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.
