416 SPECIAL RESULTS IN THE URANOLOGICAL 



between the front part of the constellation of the Ship and 

 Sagittarius ; or, to name portions of the heavens visible in 

 our own hemisphere, between Aquila and Cygnus. 



On the whole, however, the brightness of the Zodiacal 

 Light did not appear to me to increase sensibly with the 

 elevation of the observer's station, but rather to depend prin- 

 cipally on internal variations, i. e. on greater or less degrees 

 of luminous intensity in the phsenomenon itself. I even 

 remarked, when in the Pacific, a counter- glow, like that of 

 sunset. I have said, depending " principally" on internal 

 variations, because I by no means deny the possibility of a 

 concurrent influence from the greater or less transparency of 

 the upper strata of the atmosphere, while in its lower strata 

 my instruments indicated no hygrometric changes, or some- 

 times such as would have had an opposite tendency. Ad- 

 vances in our knowledge of the Zodiacal Light may be 

 most hopefully looked for from the tropical regions, where 

 meteorological processes attain the greatest degree either 

 of uniformity or of regularity in their periodical variations. 

 The phsenomenon is there perpetual : and a careful com- 

 parison of observations at stations of different elevation, 

 and under different local circumstances, would enable us 

 to decide, by the aid of the calculus of probabilities, what 

 we ought to ascribe to cosmical luminous processes, and 

 what to mere meteorological influences. 



It has been stated more than once, that for several suc- 

 cessive years scarcely any Zodiacal Light, or only a very 

 faint trace of it, has been seen in Europe. Does the light 

 appear proportionally enfeebled in the equatorial zone in 

 years when this is the case ? Such an investigation, how- 



