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