“The Cairngorm water is all clear. Flowing from granite, with no peat to darken it, it has never the golden amber, the ‘horse-back brown’ so often praised in Highland burns. When it has any colour at all, it is green, as in the Quoich near its linn. It is a green like the green of winter skies, but lucent, clear like aquamarines, without the vivid brilliance of glacier water. Sometimes the Quoich waterfalls have violet playing through the green, and the pouring water spouts and bubbles in a violet froth.”