Attempt to apply instrumental measurement to the Zodiacal Light

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                                observed unequal size of the two sides. Were the light stationary, 
then the greatest & least lengths and brightnesses should occur at 
the same time in successive years; because on arrearing again at 
the same points of its orbit, the earth should see again the same 
parts of the Zodiacal light pointing to the same direction in space; 
but as already stated the contrary to this has been observed. 
The greatest elongation observed was 79[degree], & the least 
50[degree], but from the varying circumstances & positions in which 
the observations were made, the short period of time over which 
they extend, and the distance of the place from the equator, to=
=gether with the small number of opportunities which 
these conditions afforded, no numerical results of much accuracy 
can be derived from them alone; but some advantage may 
be gained by comparing them with the results of former observers. 
The number, however, of these i.e., of actual observers, is comparatively 
small, and they are all very recent; for strange to say, no notice 
of the Zodiacal Light is found amongst the writings of astronomers, or natural  
philosophers until 1661. and indeed when we consider that this 
phenomenon may be described as a lenticular shaped light seen 
in the Western sky after sunset, and in the Eastern before sunrise, 
with a length of about 60[degree], a breadth of 20[degree], combining with a bright=
=ness nearly equal to that of the Milky Way, a regular mathematical 
figure which makes it far more remarkable, & rising at a greater 
angle to the horizon, so as to be better seen in countries nearer the 
equator than ourselves, and being probably of as great antiquity as 
the sun itself, - truly it is astonishing that all these notabilia 
should have been passed over in the earlier ages of the world, when 
civilization flourished more to the South, and the men of ancient 
Athens and Babylon lived under a clear sky, in a genial climate, 
which invited, rather than forbade, the  contemplation of the firma=
=ment by night. 
It remained however for the inhabitants of these 
cloud-vexed Northern islands, to be the first to take notice of the 

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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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