Evening star. [volume] (Washington, D.C.) 1854-1972, 1913-06-22
THE ALPENGL0W.
Splendid Spectacle of Color Among
the Snow-Capped Mountains.
From the Scientific American

| From the Scientific American.
| Everybody who has sojourned among
| the Alps, or other snow-capped noun
| tains. must have admired the gorgeous
| coloring of the peaks at sunrise and sun
| set. Watching the splendid spectacle
| from day to day the attentive observer
I soon discovers that it is a complex phe-
| nomenon, varying greatly with the
| weather and sometimes exhibiting GER
| tain peculiaritieS that to the uninitiated
| are decidedly mysterious.
| In fine weather the following sequence
| of events may he noted: When the sun
| has sunk nearly To the observers horizon.
| the peaks to the eastward begin to have
a reddish or golden hue This fades grad
| ually. hut in few minutes, when the
| sun is a little below the observers hori-
zon. but the peaks are still bathed in
| direct sunlight. an intense red glow be-
/ gins down the slopes and moves upward
| to the SUBMITS. This is identical with
the rosy twilight arch that in clear
weather rises from the eastern horizon
as the sun sinks below the western; AMI
ii is bordered below by the blue shadow
of the earth. Now, for a few minutes.
the peaks are i'll the earth-shadow; their
rocks and SHOWS assume a livid appear
ance. aptly described by the inhabitants
of the vale of Chamounix, whence the
phenomena in question are well seen
"teinte CddaVereuSe.
Presently occurs the remarkable phe-
nomenon known as 'recoloration' or ,''af-
/ terglow. In ChamouniX it is called the
resurrection of Mont Blanc" The peaks
! from which all color had faded. again as
sumo rosy tint: but this time gradually.
and without any sharp line of demarca-
| ton between the glow and the shadow
| beneath The recoloration is by no
| means daily occurrence-in fact it Is
! rather II varies Orpat1y
| i'm appearance and duration Sometimes
| IL lasts until an hour after sunset. and 1t
passes away from below upward. Very
| rarely faint second recoloraton may be
| seen. All these phenomena may he seen,
| in reverse order. at sunrise though they
are less common then than at sunset.
| They are known, collectively. as the
! "Alpenglow
| The recolCration of the Alps has been
varously explained. but there seems to
| be little doubt that it is due, at least
| principally, to the reflection from the
peaks OF the rosy glow which forms i'm
| the western sky after sunset. known as
| the purple light. and which is some
times intense enough to constitute sec
| ondary luminous source. The diffuse ap-
pearance of the recoloration, as compared
with the well defined zone OF rosy light
| that rests upon the peaks while the
latter are still in direct sunlight is ex-
| planned by the broad eXpaRSe of the
| purple light" as compared with the
small disk of the sun. Sometimes the
sky itself q. e.. the fine dust i'm the
| upper atmosphere, reflects the purple
light giving rise to a second purple
light for observer situated at a suit
able angle Of vision. This in turn may
be reflected by the mountains giving the
rare phenomenon of second recolora-
ton.
y rival explanation of recoloration. pro-
posed by AmSleT. according to which the
lnhenOmpnnO is due To rand change in
! the refractive index of the lower air,
owing To cooling after sunset is not
| now accepted, chiefly for two reasons,
viz. il fails to account for the CORE
| spending sequence of phenomena before
sunrise. and II assumes stronger con-
/ trasts of temperature in the vertical than
/ have generally been found to occur. 1t
. is not impossible. however. that the pro-
/ cess described by Amsler may sometimes
cooperate in producing the AlpenglOw
at sunset.