Attempt to apply instrumental measurement to the Zodiacal Light

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                                'equal to that of the moon in her first quarter. Towards ten oclock, 
in this part of the Pacific, the Zodiacal light usually becomes very 
faint, and at midnight I could only see a trace of it remaining. 
On the 16th of March, when its brightness was greatest, a mild re=
flected glow was visible in the east.'" 
But as to the idea of the body being in the shape of a ring, 
I cannot find and grounds all through the Baron's writings 
for the maintenance of such an opinion, though I have especially 
searched them: and the idea seems rather to spring from his peculiar 
notions of the rationale of the creation of the solar system, an un=
=fathomable mystery, but which it would appear that he thinks 
he fully understands, and that his opinions thereon have been 
fully proved and demonstrated to be true; for he describes in some 
parts of his works the formation of the planets and satellites out of 
certain nebulous rings, of which the Zodiacal light it the last ex=
=tant: and dismisses very complacently the peculiar conditions and 
circumstances of such rings, from the habitudes which we now observe 
the so-called <u>resulting<\u> planets and satellites to have. 
He describes also several anomalous features, as that sometimes 
it did not appear for three quarters of an hour after sunset, though 
the twilight had been for some time ended, that then it appeared 
suddenly, and continued long of very great brightness, that at 
other times it would continue to shorten and lengthen many 
degrees in a few minutes, and have an undulatory sort of motion. 
But these peculiarities, when not accounted for by the Atmos=
=pheric circumstances of which he himself takes notice, seem rather 
to be produced in the eye of the observer, by reason of the extreme 
faintness of the object to be observed, by the length of <s>a<\s> time that 
a retina, - which has been initiated by watching the setting sun, 
or even when acted on by ordinary daylight, - requires to recover 
its full degree of sensitiveness, as well as by the deceptive phan=
=tasmagoric effect produced on the nerves when strained to a 
greater extent than they can well bear. 
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Manuscript details

Charles Piazzi Smyth
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Cite as

Attempt to apply instrumental measurement to the Zodiacal Light , 1840. From The Royal Society, AP/30/18



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