96 FRAGMENTS OP SCtENCtt. 
ized, is not directly affected by the Nicol. It will also be 
understood that it is not the interposition of the haze as an 
opaque body that renders the mountains indistinct, but 
that it is the light of the haze which dims and bewilders 
the eye, and thus weakens the definition of objects seen 
through it. 
The results have a direct bearing upon what artists call 
"aerial perspective/' As we look: from the summit of Mont 
Blanc, or from the lower elevation, at the serried crowd of 
peaks,especially if the mountains be darkly colored cov- 
ered 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 
distant 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 oppo- 
site side of the Ehone valley, and between both we have 
the blue haze referred to, throwing the distant mountains 
far away. But at certain hours of the day the haze may be 
quenched, and then the Massa ridge and the mountains be- 
yond the Ehone 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must be withdrawn from the mountains and from the trees 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 
itself. We live in the sky, not under it. 
These points were further elucidated by the deportment 
of the selenite plate, with which the readers of the forego- 
ing pages are so well acquainted. On some of the sunny 
days of August the haze in the valley of the Ehone, as 
looked at from the Bel Alp, was very remarkable. Toward 
evening the sky above the mountains opposite to my place 
of observation yielded a series of the most splendidly col- 
