I INTRODUCTION. 



cured from that institution a nine-inch celestial globe ; and this, with an odd number of the 

 American Journal of Science, containing some remarks by Professor Olmsted on the Zodiacal 

 Light, and two of Nichols's works on Astronomy, were my only helps. The globe, published by 

 the "Society for the Diffusion of Useful Knowledge" in England, proved, however, to be of 

 uncommon accuracy throughout. 



This very lack of the means of information, however, bad its advantages ; for I was thus kept 

 from being drawn into the vortex of former opinions, or of being borne down by the influence of 

 great names ; and when, by and by, I became deeply interested in this- subject, I was left to 

 pursue my observations all the more carefully, and with the greater jealousy of mistake, from 

 the fact that I had nothing to depend on but myself. Thus the data in this book are inde- 

 pendent of all preconceived opinions, and I may add, also, in a great measure, of any opinions 

 by myself; for I determined, in the first place, to get facts; and when I saw how frequently 

 the dimness and indefiniteness of the Zodiacal Light would admit of self-deception, even where 

 the intentions might be the most honest, I became jealous of myself to such a degree as not to 

 allow myself, except in very rare cases, to refer back, or to compare present observations with 

 those of any previous date. I also repressed in myself, as strenuously as I could, until the 

 very last of the cruise, all disposition to form hypotheses ; for I saw that my opportunities for 

 observation were uncommonly favorable, and I wished to be faithful to my trust as an observer, 

 and to have facts that could be relied on, whithersoever they might lead. The consequence 

 of all this is, however, that there are incongruities and contradictions here and there in these 

 lines of Zodiacal Light, or, at least, what appears to us to be such. Had I allowed myself to 

 refer back, and so to guide myself along by former data, or to theorize, I could have made the 

 results more symmetrical and more harmonious ; but I declined seeking for symmetry, or even 

 consistency, at such a risk. An hypothesis to go upon is often useful in sharpening observa- 

 tion ; but it may also warp the mind and mislead, and I thought it would be too dangerous 

 here; and my observations are not only independent of hypotheses, but, from the causes just 

 stated, are independent also of each other. 



It may seem to be, and perhaps is, inconsistent with the remarks just made, to say that, at 

 an early period, the idea of a nebulous ring around the earth came up in my mind as applying 

 more than any other to the case, and that it remained there to the last. I could not help think- 

 ing; and in those long, silent, night watches, thoughts of this kind would often be busier than 

 I wished them to be. But I still tried to be faithful to my work as an observer, not a theorist ; 

 and if I swerved from this dirty, I am not conscious of it, except in a single case. That excep- 

 tion I regret. It was where I had seen a light in the evening, ascending high in the eastern 

 sky, (see July 7th, 9th, and August 5th, 1853,) and noticed it several times again the follow- 

 ing year ; but, concluding that it ought not to be the Zodiacal Light, I failed to make record of 

 it at the latter period.* 



My first observations were of an awkward, and for a long time they were of a very desultory, 

 kind. I contented myself with making records of having seen the Light, and with giving its 

 boundaries, by written descriptions, in a general way. But the necessity of precision soon 

 showed itself; and, as I went on, of yet still greater precision ; and I then constructed a star-chart 



o P. S. Brooklyn. I have regretted this still more since reading Baron Humboldt's remarks on this eastern light, in 

 the Astrommische .\".c, ',,,,/,/,/, x,,. 939 ; and also an article by Theodore J. C. A. Brorsen, in No. 998 of the same periodi- 

 cal. The latter calls it by a very appropriate name, gegenschein (a shining opposite), and informs us that he made continu- 

 ous observations on it for about two years. For a more extended notice of his observations, see the annotations in this 

 book, No. 42. 



