VIII INTRODUCTION. 



The subject appears, however, to have been entirely neglected by the officers and savans of 

 La Bonite. 



Soon after the wonderful meteor-shower of 1833, the subject of the Zodiacal Light was 

 revived ; and observations were made connected with the query, whether that extraordinary 

 display of meteors was not owing to the passage of our earth, and its atmosphere, through the 

 substance aifording that Light. Our own eminent countryman, Professor Olmsted, with other 

 gentlemen, at different observatories, were diligent observers, and with various results; going 

 little, however, beyond the question of the meteoric shower and its cause. Biot, in France, 

 came out as an advocate of this theory, and attempted to show that the shower was owing to 

 the earth's passing, at that time, near the node of the Zodiacal Light. This led J. C. Houzeau 

 to calculations, in order to see whether the nodes of the Zodiacal Light and sun do actually cor- 

 respond ; and, in the AstronomiscJie Nacliriclden of 1844 he has published the result of his 

 examinations of fifty-eight observations on this Light, by nine of the most diligent observers, 

 including Mr. Herrick, of Yale College, whose industry on this subject has never been excelled 

 by any one. Houzeau thinks that, from these examinations, he has shown that these nodes are 

 different; and that therefore "the supposition of the existence of this Light in the plane of the 

 sun's equator does not satisfy the observations made." The closing sentence of his very inter- 

 esting article gives the first intimation, and the only one that I have met with, that the Zodia- 

 cal Light has a near connexion with our own globe; and I will quote it at length. He says: 

 "One is struck, without doubt, with the near approach which our elements show between the 

 line of nodes of the Zodiacal Light, and that of the nodes of the terrestrial equator upon the 

 ecliptic. This circumstance, as far as it is verified, may cast a new day upon the causes of this 

 luminous phenomenon causes which are, it may be, more local than have been hitherto 

 supposed." 



During the next year (i. e. in 1845), there was published in Comptes Rendus (vol. 16, pp. 

 687-8,) a letter from Mon. Ad. Matthiesson to Arago, detailing some experiments made at 

 Paris, to ascertain whether there was heat connected with the Zodiacal Light. I give his 

 remarks for whatever they may be considered worth. He says: "Monday, 27th March, at eight 

 in the evening, a concave mirror, of one metre in diameter, highly polished, with a thermome- 

 ter in air, very sensitive to heat, did not indicate any elevation of temperature. An elevation, 

 however, was perceptible when the axis of the mirror was directed to the Zodiacal Light. 



"The next evening I placed an excellent thermo-electric pile of Mr. Ruhmkopf, of twenty- 

 five pairs, in a spot slightly hollowed out, between the Arc de I'Etoile and the Bois de Boulogne. 

 The needle of the galvanometre rested at zero, when the pile, fortified with its cone condenser, 

 was turned upon the polar star. Turned towards the tail of the comet above Orion, it remained 

 at zero; towards the nucleus, the needle indicated two degrees. But the impression of heat 

 gradiially increased when the pile was turned towards the Zodiacal Light, after passing the tail 

 of the cornet: towards the Pleiades, 10 of deviation; towards the base of the Zodiacal Light, 

 12 ; above the point where the sun had set, 5. At 9 o'clock, the same result for the comet; 

 towards the Pleiades, 8 ; towards the base of the Zodiacal Light, 12 ; above the point where 

 the sun had set, 3. At 9 h 30 m , 7, 10, 2, and the same result for the comet," 



He thinks it, however, doubtful whether the increased temperature indicated when turned 

 towards the Zodiacal Light, was owing to the substance giving that light itself, or to heat left 

 in that portion of our atmosphere by the sun lately set. 



