66 STATEMENT AND EXPOSITION OF 



made ample records with the particularity which the case required. It was a 

 great satisfaction, after my return home, to find tliat Baron Humboldt had observed 

 the same thing while in southern latitudes, though he thought it more probable 

 that it was owing to ' processes of condensation going on in the uppermost strata 

 of air, by which the transparency, or rather the reflection of light, may be modified 

 in some peculiar and unknown manner.' My records, however, will show that 

 there is a regularity of appearance at the closing off of these pulsations, which proves 

 that they do not belong to so uncertain a cause as atmospheric changes, but to the 

 nebulous substance itself. They seem to intimate a great internal commotion in 

 the nebulous matter, for they were too rapid to be occasioned by irregularities in 

 its exterior surface. 



"I noticed them again the following year, but must refer the reader to my 

 records and charts. The changes were a swelling out, laterally and upwards, of 

 the Zodiacal Light, with an increase of brightness in the light itself; then, in a 

 few minutes, the shrinking back of the boundaries, and a dimming of the light; the 

 latter to such a degree as to appear, at times, as if it was quite dying away; and 

 so back and forth for about three-quarters of an hour ; and then a change still 

 higher upward toward permanent bounds." 



(93) That these pulsations should be real seems not incredible in the instance 

 of a substance having, as it would seem, a density even less than that of the 

 material which exhibits the rapid changes of intensity, etc., of the aurora borealis. 

 The girdle, moreover, would have a very nearly constant position with respect to 

 the earth and the moon — hoth magnetic ; and the earth in a relatively rapid rota- 

 tion} 



(94) It would seem most probable that the middle plane or equator of the girdle 

 should nearly coincide with the plane of the moon's orbit; but even in that case, 

 the more intense illumination by transmitted light would be in directions nearly 

 parallel to the plane of the ecliptic. That, and the local illumination, (75), ascer- 

 tained and described by Mr. Jones, would together make it difficult to determine 

 where the middle plane maybe situated; though some observations of the "gegen- 

 schein" might seem to make it the same with the plane of the moon's orbit. 



The position of the vertex of the Zodiacal Light would need to be more carefully 

 scrutinized, and compared with that condition. 



Such being the state of things, observations for parallax must, withal, most 

 probably continue to be unsuccessful. 



(95) As a summation of the consistencies of the hypothesis of a nebulous girdle 

 revolving around the earth in the same time and general direction with the moon, 

 and exhibiting the phenomena of the Zodiacal Light, we have: — 



1. That it provides a conservative force for the maintenance of such an 

 appendage. 



' But it would be more difflnnlt to nndcrstand and account for these special phenomena presented 

 by the material in question, if it were directly a solar, instead of a terrestrial, appendage. 



I 



