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270 FRAGMEN TS OF SCIENCE.

Nicol. It will also be understood that it is not the interposi-
tion of the haze as an Opaque body that renders the moun-
tains indistinct, but that it is the light of the haze which
dims and bewilders the eye, and thus weakens the defini-
tion of objects seen through it.

The results have a direct bearing upon what artists call
“ aerial perspective.” As we look from the summit of the
Aletschhorn, or from a lower elevation, at the serried crowd
of peaks, especially if the mountains be darkly colored——
covered with pines, for example—every peak and ridge is
separated from the mountains behind it by a thin blue haze
which renders the relations of the mountains as to distance
unmistakable. When this haze is regarded through the
Nicol perpendicular to the sun’s rays, it is in many cases
wholly quenched,-because the light which it emits in this
direction is wholly polarized. When this happens, aerial
perspective is abolished, and mountains very differently dis-
tant appear to rise in the same vertical plane. Close to the
Bel Alp, for instance, is the gorge of the Massa, and beyond
the gorge is a high ridge darkened by pines. This ridge
may be projected upon the dark slopes at the opposite side
of the Rhone valley, and between both we have the blue
haze referred to, throwing the distant mountains far away.
But at certain hours of the day this haze may be quenched,
and then the Massa ridge and the mountains beyond the
Rhone seem almost equally distant from the eye. The one
appears, as it were, a vertical continuation of the other.
The haze varies with the temperature and humidity of the
atmosphere. At certain times and places it is almost as
blue as the sky itself; but to see its color, the attention ,
must be withdrawn from the mountains and from the trees
which cover them. In point of fact, the haze is a piece of
more or less perfect sky; it is produced in the same man-
ner, and is subject to the same laws, as the firmament it-
self. We live 'in the sky, not under it.

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