ZODIACAL LIGHT. ISI 



pertain to the outer world. This awakens, by the power of 

 the imagination, a meditative, spiritual train of thought, where 

 the untutored mind perceives only scintillations of light in the 

 firmament, and sees in the blackened stone that falls from the 

 exploded cloud nothing beyond the rough product of a power* 

 ful natural force. 



Although the asteroid-swarms, on which we have been led, 

 from special predilection, to dwell somewhat at length, ap- 

 proximate to a certain degree, in their inconsiderable mas.s 

 and the diversity of their orbits, to comets, they present this 

 essential difference from the latter bodies, that our knowledge 

 of their existence is almost entirely limited to the moment of 

 their destruction, that is, to the period when, drawn within 

 the sphere of the Earth's attraction, they become luminous 

 and ignite. . 



In order to complete our view of all that we have learned 

 to consider as appertaining to our solar system, which now, 

 since the discovery of the small planets, of the interior comets 

 of short revolutions, and of the meteoric asteroids, is so rich 

 and complicated in its form, it remains for us to speak of the 

 ring of zodiacal light, to which we have already alluded. 

 Those who have lived for many years in the zone of palms 

 must^retain a pleasing impression of the mild radiance with 

 which the zodiacal light, shooting pyramidally upward, illu- 

 mines a part of the uniform length of tropical nights. I have 

 seen it shine with an intensity of light equal to the milky way 

 in Sagittarius, and that not only in the rare and dry atmos- 

 phere of the summits of the Andes, at an elevation of from 

 thirteen to fifteen thousand feet, but even on the boundless 

 grassy plains, the llanos of Venezuela, and on the sea-shore, 

 beneath the ever-clear sky of Cumana. This phenomenon 

 was often rendered isspecially beautiful by the passage of light, 

 fleecy clouds, which stood out in picturesque and bold relief 

 from the luminous back-ground. A notice of this aerial spec- 

 tacle is contained in a passage in my journal, while I was on 

 the voyage from Lima to the western coasts of Mexico : " For 

 three or four nights (between 10^ and 14° north latitude) the 

 zodiacal light has appeared in greater splendor than I have 

 ever observed it. The transparency of the atmosphere must 

 be remarkably great in this part of the Southern Ocean, to 

 judge by the radiance of the stars and nebulous spots. From 

 the 14th to the 19th of March a regular interval of three 

 quarters of an hour occurred between the disappearance of the 

 sun's Usk in the ocean and the first manifestation of the zodi- 



