OBSERVATIONS ON THE ZODIACAL LIGHT. 



No. 42. 



AUGUST 5th, 1853 : MOBNLNG ; also Eastern Light the evening previous. - 



Lat, at 4 a. m., 21 31' N. : Lon. 121 3' E. 



Sun rose? 5A. 3!l/. 

 Stronger Li.^lit at Hi. : Diffuse. S/i. 30m. and 11A. p. m., of 4th, and 2A. and 5/i. of 5th. 



At 8" 30 m , last evening, I turned to the eastward, and found there an appearance much like the upper extremity 

 of the usual Zodiacal Light. Its boundaries are given in this morning's chart. Distrustful of my judgment, I got 

 one of the quartermasters to look, who readily made it out and deliued its boundaries -the same as they appeared 

 to me. Its brightness was equal to that of the Milky Way about 1(J Aquihe (marked a a a at the upper end of 

 the chart). It could not be confounded with the Milky Way, 'between which and it there was a decidedly dark 

 space ; as there was, also, on the other side of the Milky Way, between the latter and the top of the Western Zodiacal 

 Light, then in sight. 



At II 1 ' went on deck, and found the same appearance, only it had changed its place, and was larger, as in the 

 chart: the brightness was about equal to that of half-past eight. 



At 2", on deck again; and now the Zodiacal Light was very decided. There could be no mistake about it. At 4", 

 another observation, and now had the Stronger Light. I cannot assert that the Eastern Light, at 8" SO" 1 and II' 1 p. 

 m., was the real Zodiacal Light; but it was much like it. 



[ Brooklyn, 1856. The above remarks, with others of previous date, on this Eastern Light, will show my exceeding- 

 caution about admitting any tiling new, and my fears about embarrassing the true observations with any thing uncer- 

 tain. A letter from me, published in May, ultimo, in the American Astronomical Journal, has led Baron Humboldt 

 to quote from his unpublished MSS., in which are records of a similar light seen by him in the cast, in the evenings 

 of the 17th and 18th of March, 1803, in hit. about 1:5 N. ; which, however, lie supposes to be only a reflection from 

 the Western Zodiacal Light, then shining with exceeding brilliancy. (See Astronomisclie Nachrichten, No. 980.) In 

 No. 998 of the Astro. Nachrichli'ii, is another paper on this subject by Mons. Theo. J. C. A. Brorsen, of Serptenberg, 

 in Germany, who calls this Eastern evening light by the appropriate name of gegenschein (a shining opposite), and 

 informs us that he had seen it regularly at that place during the two previous years. His paper concludes as follows: 

 "The ycijeitscJtcii) is visible, not only at the vernal, but also at the autumnal equinox; at the former time more dis- 

 tinctly. A faint trace of it becomes visible in January, from which time it grows stronger till March, when, and in 

 April and the early part of May, it is quite distinct and broad. A much smaller and weaker gegenschein appears in 

 Sept ember, October, and November. I have become convinced, by frequently repeated observations, that, in both 

 cases, the brightest part of the gegenscltcin is directly opposite the place of the sun; so that a calculation of the great- 

 est light frequently coincides to a degree with the point of opposition to the sun. The observations proved that the 

 vernal </a/enschein, about the middle of April, joins the Westerly Zodiacal Light by a strip or belt of light, which is, at 

 first, very weak, but becomes by degrees more luminous ; the autumnal gegenschein appears, in the first part of No- 

 vember, to be elongated along the ecliptic by a weak zone of light as far as the western horizon, which zone of light 

 is, by degrees, transformed, by increasing luminosity and more distinct basis, into the well-known phenomenon of the 

 Western Zodiacal Light. From this time to the commencement of March, its apex remains almost stationary in the 

 region of r 1 and r 2 Arietis. Both gegenschein could be seen here, at the same season, on every clear evening; and 

 even distinctly in the light of the new moon."] 



