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XXXUL —Contributions to a Knonledge of the Phenomena of the Zodiacal Light. 
By Professor C. Prazzt Smyru. 
“(Read February 7, 1848.) 
Wainy preparing to make a night journey over one of the plains of South Africa. 
in the month of June 1843, a friend called my attention to the peculiar appearance 
of the sky in the west, as offering a very decided proof, “ agreeably with theory,” 
that there was no “ Solar atmosphere” to be seen at that season of the year. 
On looking in the direction mentioned, the last portion of the twilight was 
just visible, and forming a peculiarly level line above the place where the sun had 
set, for an extent in azimuth, of perhaps 40°, and at a height of about 5°. All the 
gorgeous colours which had attended the setting of the sun had long since vanished, 
and there only remained. sufficient light within the flattened are described, to 
make the space included between it and the horizon appear light blue, while all 
the rest.of the sky had attained a deeper colour, nay was almost black, and thickly 
spangled with small as well as large stars. 
_ There most decidedly was not then any symptom of the so-called “ way of 
the twilight shooting upward.” But as soon as the last illuminated portion 
of the western sky had set, the phenomenon, i.¢., the zodiacal light, appeared 
in an, unmistakeable manner,:rising up in the ecliptic, to a height of 50°, with a 
breadth of perhaps 12° at the horizon; and forming, with the vast extent of its 
illuminated surface, and the regularity of its contour, one of the most remark- 
_ able objects in the starry sky. The form was that usually described, viz:, a wedge 
_ ~pointing upwards, with curved sides, and of excessively indefinite outline; but 
_ still, as far as could be judged, free from any irregularities ; while the light, which 
_ Was more delicate and transparent than that of the milky way, increased in 
- intensity transversely from either side to the central longitudinal axis; and 
augmented also in the axis, from the apex downwards, until overpowered by the 
haze on the horizon. 
_ | Now, two circumstances worthy of notice, were pointed out by this night's ob- 
_ servation, jirstly, that persons did not always know exactly when to look for the 
_ zodiacal light, nor what sort of object to expect; and, secondly, that the theory 
was greatly in error; and, for an astronomical matter, grievously wrong. Both 
_ classes of mistakes may have been brought about in no small degree by the inju- 
dicious mixing up of erroneous theoretical and speculative views with the simple 
nomenclature of the phenomenon. All that can he asserted from a single obser- 
_ vation, and, perhaps indeed, from all the observations that have been made, up to 
the present time, is that a light appears in the zodiac, and if it be called “ the 
VOL. XX. PART Ill. 6Q 
