374 ANNUAL OF SCIENTIFIC DISCOVERY. 



ON THE ZODIACAL LIGHT. 



The following is a paper on the Zodiacal Light, read before the American 

 Association, Providence Meeting, by Keverend George Jones, U. S. N. : 



Only some vague notices of the zodiacal light occur in ancient authors be- 

 fore it is distinctly and briefly mentioned by Chauldry, in 1661. It was first 

 carefully observed by Cassini, an Italian by birth, at the Observatory of Paris. 

 He thought it an emanation of the sun. His associate, Tacio, thought it a 

 ring around the sun. Miran, in 1731, thought it an atmosphere connected 

 with the sun. In all subsequent speculations no new observations after Cas- 

 sini's were used till 1832. In 1844 Biot observed that the nodes of the zodi- 

 acal light did coincide with those of the earth, and suggested that it might be 

 more local than had been supposed. He found that it gave much more heat 

 than the tail of a comet did. No observations had been made previous to 

 those of Mr. Jones except in northern latitudes. These were made at sea 

 on a voyage to China. The zodiacal light appears best when it is on the 

 ecliptic. When at the summer solstice and on the tropic of Capricorn the 

 zodiacal light was visible from 11 to 1 in both horizons at once with their 

 apices approaching each other. In the center of the zodiacal light is a con- 

 densed part with a boundary of its own. On this voyage, January 31, 1854, 

 at Loochoo, he first noticed the pulsations of intensity in the space of a min- 

 ute or two that it exhibits on some occasions. He made 331 sets of observa- 

 tions. He found that if by the revolution of the earth he receded from the 

 ecliptic, the zodiacal light moved a little in the same direction, and vice versa. 



Mr. Jones then stated that the following facts he had noticed could be ex- 

 plained by one supposition, viz., that of a nebulous ring surrounding the earth ; 

 the following are the results of his observations : 



1. This light can not be from any body involving us in its matter, else we 

 could not get boundaries to it any more than we could to a mass of fog or a 

 column of smoke in which we were involved. "We must be apart from it in 

 order to get bounds. 



2. It can not be from a planetary nebulous body revolving around the sun, 

 but must be from a nebulous ring ; for it is to be seen very morning and 

 evening in the year, when the moon or clouds do not interfere, which could 

 not be the case were it any thing else than an unbroken ring. 



3. If a ring, with the sun for its center, it can not be within the orbit of 

 our globe, for then it could not be seen simultaneously over the eastern and 

 western horizon at midnight, the spectator's horizon then extending far above 

 it on either side ; nor could its vertex ever be in the spectator's zenith, or 

 indeed any great distance above his horizon, which is contrary to facts. 



4. Is it a solar ring extending beyond the earth? On this subject I must 

 refer to the data afforded by these observations, for it is only from facts 

 that we are able to argue in the case. Any one examining these data will 

 see, I think, that the lateral changes from hour to hour in the boundaries 

 of the zodiacal light especially toward the horizon, could not have taken 

 place in a ring so distant as a solar ring would have been at the point where 



