xvi.,
1843, Avril, p. 687.)
Must we suppose that changes are actually in progress in the nebulous ring?
or is it not more probable that, although I could not, by my meteorological
instruments, detect any change of heat or moisture near the ground, and
small stars of the fifth and sixth magnitudes appeared to shine with equally
undiminished intensity of light, processes of condensation may be going on
in the uppermost strata of the air, by means of which the transparency, or
rather, the reflection of light, may be modified in some peculiar and
unknown manner?
p 143
An assumption of the existence of such meteorological causes on the confines
of our atmosphere is strengthened by the "sudden flash and pulsation of
light," which, according to the acute observations of Olbers, vibrated for
several seconds through the tail of a comet, which appeared during the
continuance of the pulsations of light to be lengthened by several degrees,
and then again contracted.*
[footnote] *"What you tell me of the changes of light in the zodiacal
light, and of the causes to which you ascribe such changes within the
tropics, is of the greatr interest to me, since I have been for a long time
past particularly attentive, every spring, to this phenomenon in our
northern latitudes.
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