Attempt to apply instrumental measurement to the Zodiacal Light

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                                phenomenon; & so supply another instance of the indomitable perse=
=verance of an iron race overcoming all the untoward obstacles of an 
unpropitious position; and rising superior to other races revelling in 
all the luxurious advantages of nature. 
Claims have been put up for Kepler and Descartes, as 
being the original discoverers of the Zodiacal Light; but the passages in 
their respective works (Kepler's Epit. Astron. Copernicanae T.1. p57 & 
T.2, p.893.)(Descartes, Principes 3, art. 136 & 137) are so very meagre and 
obscure, that they require all the knowledge of the phenomenon acquired 
up to the present day, to be applied to these, to make them mean anything. Mairan, with whose theory, Kepler's fancy seems to 
agree, when discussing in 1754, the history of the phenomenon, gives 
the German full credit: but Humboldt, in 1844, with different 
theoretical views, dismisses the case of his countryman in a very summary way. 
An earlier claim still has been brought forward, 
on account of the mention in a letter from Rothmann to Tycho 
Brah[e acute], - that in the spring, the twilight ceased not till the 
sun was 24[degree] below the horizon, and as the true twilight would 
have ceased long before the Sun was so low, - it is contended that 
Rothmann must have seen the Zodiacal Light, though without 
remarking anything peculiar in it, or different from the ordinary 
course of the evening. 
So that the first satisfactory and clear description is still 
that of Childrey in 1661, already alluded to. "There is another thing", 
says he in his Britannia Baconica, p.183, "which I recommend to 
the observation of mathematical men: which is, that in February, and 
for a little before and a little after that month (as I have observed 
for several years together) about 6 in the evening, when the twilight 
hath almost deserted the horizon, you shall see a plainly discernible 
way of the twilight, striking up towards the Pleiades, and seeming 
almost to touch them. It is so observed any clear night, 
but it is best <u>ill[a circumflex]c nocte<\u>. There is no such way to be observed 
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Charles Piazzi Smyth
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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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