XIV INTRODUCTION. 



same thing, as will be seen by reference to his annotations quoted in this book, fronting the 

 chart 351. 



I now, however, come to what may perhaps be the most important of all these observations ; 

 but a part in which my observations are meager, compared with the rest. I had, at an early 

 period, queried whether the moon might not give a Zodiacal Light, and had given attention to 

 the subject; but, probably, had looked too high up in the sky, and, at all events, had failed 

 to see anything of the kind. But, one evening, when I was finishing some boundaries from the 

 western sky, the quartermaster on duty said to me: "The moon is going to rise;" and, on 

 crossing the deck, I was struck at once with the resemblance between the light then showing 

 itself in the eastern sky and the morning Zodiacal Light, in every thing except its elevation. 

 In breadth, in the peculiar boundaries laterally of the Zodiacal Light, and in coloring, it was 

 all the same ; and, in its subsequent rapid changes, it still kept strictly within the Zodiacal 

 Light bounds. The following night I was prepared to make records; and I never failed after- 

 wards to watch for recurrences of such light. But they did not often present themselves ; for 

 the ecliptic should be at a high angle, otherwise the light is apt to be so scattered along the 

 horizon as to be unsatisfactory. It also happened, that we almost always had cloudy weather 

 when such observations are most desirable namely, at the full of the moon. For what was 

 done on the subject, I must refer to the charts towards the close of this book, inviting attention 

 more particularly to the observations of February 14th and 15th, 1854, and also to that of 

 March 18th, of the same year, Nos. 331, 332, 335. In the last case, the Light appears to have 

 extended far up (78) into the sky. 



On two occasions March 6th, and December 25th, 1854, I had also an undoubted joint sun 

 and moon Zodiacal Light. That is, when, the moon was about its first quartering*, and, at the 

 time of the observations, about 63 above the western horizon, a bright streak appeared in the 

 western sky, along the ecliptic; the joint light from the sun and moon, reflected from the nebu- 

 lous matter, being apparently sufficient to overcome the bright moonlight in our atmosphere, 

 and thus to make itself manifest. On both occasions I brought other persons to look (in the 

 latter case, the captain and several other officers), whom I got to draw boundaries which corres- 

 ponded to my own view of the subject. The latter occasion was also the more striking, because 

 the streak of light did not stretch up exactly toivards, but to one side of the moon, that satellite . 

 having then a southerly latitude of four and a half degrees. 



The observations here given commence on the 2d day of April, 1853 ; for, although I had 

 been a careful observer since December 22d of the previous year, I consider the interval as 

 having been necessary in order to gain experience, and I have consequently rejected all up to 

 the period mentioned. My first intention was to reject still more, and to commence this pub- 

 lication with June of that year ; but the extraordinary interest of some of the observations in 

 April, and the great care which I took in them to be precise as well as correct, have led me to 

 insert them. The unbroken series commences at No. 10, June Y, 1853. From that time, till 

 our arrival in New York on 22d April, 1855, every observation is recorded; and, except on 

 Sunday, I never once failed to have observations, if the moon or clouds did not prevent. 



Of the whole body of observations, however, I consider the last as more entirely reliable than 

 the first; for I was all the while gaining experience, sharpening my observations by use. As 

 an example, the reader will perhaps notice that in the morning observations of August, 1853, 

 the Zodiacal Light boundaries are not carried as high up in the sky, as in the same month of 



- Mun-U 1854, lirst quurU-i tit I livniu ] h li./. Hi. : Dr. rml.rr I>j4, do. t(>d On. Jim. 



