On the Colour of Water, 89 



of your inquiry, I shall not dwell upon tliem. In general, in examin- 

 ino- lakes and masses of water in high mountains, their colour is of 

 the same bright azure ; and Captain Parry states, that the water on 

 the Polar ice has the like beautiful tint. When vegetables grow in 

 lakes, the colour becomes nearer sea-green ; and as the quantity of 

 impregnation from their decay increases, greener, yellowish-green ; 

 and at length, when the vegetable extract is large in quantity, as in 

 countries where peat is found, yellow, and even brown. To mention 

 instances, the Lake of Geneva, fed from sources (particularly the 

 higher Rhone) formed from melting snow, is blue, and the Rhone 

 pours from it dyed of the deepest azure, and retains partially this 

 colour till it is joined by the Soane, which gives to it a greener hue. 

 The lake of Morat, on the contrary, which is fed from a lower country, 

 and from less pure sources, is grass-green. And there is an illus- 

 trative instance in some small lakes fed from the same source, in the 

 road from Inspruck to Stutgard, which I observed in 1815 (as well 

 as I recollect), between Nazareit and Rciti. The highest lake fed 

 by melted snows in March, when I saw it, was bright blue. It dis- 

 charged itself by a small stream into another, into which a number 

 of large pines had been blown by a winter storm, or fallen from some 

 other cause ; in this lake its colour was blue-green. In a third lake, 

 in which there were not only pines and their branches, but likewise 

 other decaying vegetable matter, it had a tint of faded grass-green, 

 and these changes had occurred in a space not much more than a mile 

 in length. These observations I made in 1815. On returning to 

 the same spot twelve years after, in August and September, I found 

 the character of the lakes entirely changed. The fine wood washed 

 into the second lake had disappeared ; a large quantity of stones and 

 gravel, washed down by torrents, or detached by an avalanche, sup- 

 plied their place ; there was no perceptible difference of tint in the 

 two upper lakes, but the lower one, where there was still some vege- 

 table matter, seemed to possess a greener hue. The same principle 

 will apply to the Scotch and Irish rivers, which, when they rise or 

 issue from pure rocky sources, are blue, or bluish-green ; and when 

 i'ed from peat-bogs or alluvial countries, yellow, or amber-coloured, 

 or brown, even after they have deposited a part of their impurities in 

 great lakes. Sometimes, though rarely, mineral impregnations give 

 colour to water, small streams are sometimes green or yellow from 

 ferruginous depositions. Calcareous matters seldom affect their 

 colour, but often their transparency when deposited, as is the case 

 with the Velino at Terni, and the Anio at Tivoli ; but I doubt if 

 pure saline matters, which are in themselves white, ever change the 

 tint of water. — {Salmonia^ by Sir Humphrey Davy^ p. 198.) 



