XVIII INTRODUCTION. 



H. 



A plane, pa-ssing through the centre of the Zodiacal Light, as it shows itself through the varying 

 latitudes of these observations, would correspond pretty nearly loitli the ecliptic;* but how near the 

 two planes approach to a coincidence, it seems to be yet impossible to say. Through all of 

 April, 1853, and December, 1854, there appear to be proofs of an evident crossing of the two 

 planes. Through July of 1854, the apices, in the evening, were decidedly on the northern 

 side of the ecliptic, though my latitude was only about 25 N. ; while, in September of the 

 same year, though my latitude was nearly as before, the apices were on the southern side of 

 the ecliptic, as shown by my morning observations ; the mornings then being very favorable 

 for correct observation, on account of the high angle of the ecliptic with the horizon. Again, 

 in April, 1855, the apices, and greatest body of the Light, were north of the ecliptic, even at 

 times when I was, myself, to the southward of that line ; as was the case in the first hours of 

 the evening observations, up to the 13th of that month. The following general view rather 

 shows us that there is something on this subject which may yet be learned, than that we have 

 now the materials for anything definite and certain on the subject. 



1853. April. The planes of ecliptic and Zodiacal Light cross each other. 



July. By evening observations, the apex of Zodiacal Light appears to be north of the 

 ecliptic. Morning observations are not satisfactory, either way. 



1854. March 27 to April 18, strong proofs of crossing of the planes, by both morning and 



evening observations. 



July. Apex decidedly to the northward, by both evening and morning observations. 

 September. Apices on the south, by morning observations, during this month. 

 December. Apex decidedly to the northward, through all this month. 



1855. January. Apex as decidedly to the south of the ecliptic, by both morning and evening 



observations. 

 March. Apex south of the ecliptic, by evening observations; the morning observations 



place it on the ecliptic. 

 April. Apex north. No signs of a crossing of planes. 



111. 



This Light cannot be a reflection from our atmosphere, taking its shape from that ; for this 

 atmosphere, though brought, doubtless, by the axial motion of the earth, into a somewhat len- 

 ticular shape, must have its elongation directly over the earth's equator; and the course of the 

 Zodiacal Light shows not the slightest affinity to the equatorial line. 



IV. 



This Light must be from something continuous and unbroken; not from a detached periodic body, 

 either spherical or elongated ; for, during more than two years' uninterrupted observations, I 

 never failed to see it, either evening or morning, when the moon and clouds did not interfere. 



c Which is the reason why I have chosen the ecliptic for the central line of my charts ; and why I refer so often to the 

 position of the spectator as regiyils the ertijitic. 



