XXIV INTRODUCTION. 



rated by the distance DE; at 4 h 30 m in the same place were separated only by G E, being 

 3, or 8,327,000 miles (+ the result of a-) nearer to each other than at 3 h 30 m . My own lateral 

 receding northwardly from the ecliptic, during that time, was 236 miles. 



Apply other cases, for which the same diagram will answer, with such changes as the reader's 

 intelligence will easily supply. 



January 30, 1854. Morning: lat. 26 10' N. Sun rose 6 h 48 m 30 s . In this case EN = 

 141,200,000 miles : the lateral change D G from 4 h to 5" was 27, 020, 000 miles -f the effect of 

 x. My own lateral change from the ecliptic was 345 miles. 



November 20, 1854. Morning: lat. 36 17' N. Sun rose 6 h 46 m . EN ==142,300,000 miles; 

 the lateral change, D G, from 4 h to 5' 1 was 12,450,000 miles, -f- the effect of x. My own lateral 

 change from the ecliptic was 185 miles. 



January 9, 1855. Evening: lat. 8 47' N. (The same diagram, reversing it, will answer 

 for this.) Sun set 5" 52 m . E N == 161,000,000 miles; the lateral change D G from 7" 20 m to 

 8 h 20 m was 7,740,000 miles -4- x. My own lateral change from the ecliptic was 245 miles. 



March 16, 1855. Evening: lat. 22 55' S. Sun set 6" 12 m . E N == 169,300,000 miles ; the 

 lateral change from 7" 30 m to 8 h was 5,912,000, and from 7 h 30 m to 8 h 30 m was 12,780,000 miles. 

 My own lateral change from the ecliptic in the half hour commencing from 7 h 30 m , was 85 miles ; 

 in an hour, 205 miles. 



These examples are taken as fair ones of lateral changes in the Zodiacal Light : much stronger 

 ones abound in the book, and especially when the ecliptic had a low inclination to the horizon. 



The query now arises, can such lateral changes, so uniformly observed as the evening or 

 morning advanced, agree at all with the idea of a nebulous ring giving this light at a distance 

 from the spectator of 160 or 180 millions of miles? A ring of the character supposed, it seems 

 to me, could give us a Zodiacal Light only of one uniform shape namely, with the opposite 

 boundaries receding from each other for a short distance from the apex, and then running 

 parallel, one to the other, the whole way down to the base. Nor could the hourly changes of 

 time produce any other change in these boundaries than a rising or sinking of the apex of the 

 Light; the boundaries, say at 9 o'clock, p. m., extending a little higher in the sky than at 8 ; 

 but, immediately after leaving the apex, running into those of 8, and so continued, with a 

 parallelism of the opposite sides, clown to the horizon. How different this is from the true facts 

 of the case, almost every chart in this book will testify. 



The evident and most decided connexion between these boundary-lines and the spectator's 

 place, as regards the ecliptic, is also a matter of the greatest significance in drawing our conclu- 

 sions respecting the origin of this Light. In I, of these deductions, this matter is stated in 

 detail. Now, supposing the base of the Zodiacal Light to be at a distance of 200,000,000miles: 

 how is it possible that the fact, that the spectator is a short distance north or south of the eclip- 

 tic line, can govern the reflection from the nebulous ring at that immense distance, and place it 

 on his side of the ecliptic? If he is on the north side, not only is the main body of the Light, 

 down to its base, on that side; but the lateral changes of the boundaries, as the hours pass, are 

 altogether or chiefly on that side; and so equally with the south. And so, if he is on the 

 ecliptic, or near it, the Zodiacal Light stretches equally, or nearly so, on each side of that line. 

 Also, if he changes rapidly during the night to or from the ecliptic, the boundaries of this Light 

 also change, being regulated by his motion. That the apex of the Zodiacal Light, from such a 

 ring around the sun, might be so affected by the spectator's position, is not an unreasonable 

 supposition, since the ring may approach the earth sufficiently for such a result; but, that the 



