ASTRONOMY AND METEOROLOGY. 341 



now know that such compcirison would be illusory, since the visi- 

 bility of gaseous spectra depends ujjon many circumstances which 

 it is impossible for us to determine. 



"Secondly, this spectrum is very similar to what has been noticed 

 in other comets, both by other astronomers and myself. A gen- 

 eralization of these results by induction would furnish an argu- 

 ment for the extra-planetary origin of these bodies." 



The observations of Secchi were made by comparing the spec- 

 trum of the comet with that of the planet Venus, the character of 

 ■which is well known. In the course of their prosecution he met with 

 evidences of atmospheric action which he thinks cannot be attrib- 

 uted to the earth's atmosphere, since he detected them at elevations 

 al)ove the horizon where its intiuence would have been insensible. 

 The opinion that Venus is surrounded by an atmosphere analogous 

 to that enveloping our own globe has long been held, from other 

 considerations, to possess a good degree of probability ; and of 

 this opinion Secchi's observations, should they be established by 

 future experience, will afford very satisfactory confirmation. — 

 Boston Transcript. 



This recently rediscovered comet must not be confounded with 

 another going by the same name, which has a much more ex- 

 tended orbit. It belongs to the fjimily of short period, with 

 Biela's, De Vico's, and others, which have the aphelia of their 

 orbits pretty close to the orbit of Jupiter. It seems probable that 

 the introduction of these comets within the solar system, at any 

 rate to their present position in it, is due to the action of Jupiter. 

 D'Arrest has shown that Brorsen's comet before 1842 had been 

 moving in an orbit of a very different figure from that of its 

 present one, having passed in that year very near to Jupiter, and 

 been compelled by his attractive influence to take a different path. 

 Seen in 1846, missed at the perihelion passage of 1851, again 

 seen in 1857, and again missed in 1862, it was rediscovered in 

 April, 1868 ; it will travel across the southernmost parts of the con- 

 stellations Ursa Major and Bootes, invisible to the naked eye. 



This comet has been subjected to spectroscopic analysis by Mr. 

 Huggins, with very interesting results. Two former comets, ex- 

 amined by him, exhibited in the light of their nuclei spectra closely 

 resembling those of the gaseous nebuljE, their comce apparently 

 shining by reflected light. The spectrum of the present comet, 

 however, consists of three bright bands, somewhat resembling those 

 seen by Donati in the specirum of tlic comet bearing his name ; 

 the length of the bands shows that they are not due to the stellar 

 nucleus of the comet alone, but are produced by the light of the 

 brighter portions of the coma. In one of the bands were occasion- 

 ally seen two bright lines, shorter than the band, and probably due 

 to the nucleus alone; they were not visible when the middle of the 

 comet was not upon the slit, whereas the nebulous band on which 

 they were projected continued visible as long as any part of the 

 comet, except its extreme margin, was upon the slit; there was 

 also a very faint continuous spectrum. The brightest bantl was 

 found to lie nearly in the same position as the brightest line of the 



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