Stranica 149 [149]
COLOURS IN STILL WATER — 87
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
Saone, 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 illustrative
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 Reiti.
The highest lake fed by melted snows in March, when I saw
it, was bright blue. It discharged 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 like¬
wise 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 milein 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 pine 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 vegetable matter, seemed to possess a greener hue.
The same principle will apply the Scotch and Irish rivers,
which, when they rise or issue from pure rocky sources, are
blue, or bluish green; and when fed from peat bogs, or allu¬
vial 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