The intensity
of the terrestrial light, or, rather the luminosity which is diffused,
exceeds, in cases of the brightest colored radiation toward the zenith, the
light of the Moon in its first quarter. Occasionally, as on the 7th of
January, 1831, printed characters could be read without difficulty. This
almost uninterrupted development of light
p 202
in the Earth leads us by analogy to the remarkable process exhibited in
Venus. The portion of this planet which is not illumined by the Sun often
shines with a phosphorescent light of its own. It is not improbable that
the Moon, Jupiter, and the comets shine with an independent light, besides
the reflected solar light visible through the polariscope. Without speaking
of the problematical but yet ordinary mode in which the sky is illuminated,
when a low cloud may be seen to shine with an uninterrupted flickering light
for many minutes together, we still meet with other instances of terrestrial
development of light in our atmosphere. In this category we may reckon the
celebrated luminous mists seen in 1783 and 1831; the steady luminous
appearance exhibited without any flickeriing in great clouds observed by
Rozier and Beccaria; and lastly, as Arago* well remarks, the faint diffused
light which guides the steps of the traveler in cloudy, starless, and
moonless nights in autumn and winter, even when there is no snow on the
ground.
Pages:
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425