10 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



measured in it, agreeing exactly with the lines of the solar 

 spectrum. The light of Vesuvius was sufficiently strong to 

 be observed by day, and thus to permit a direct comparison 

 of its lines with those of the spectrum of the sky. On the 

 15th of June and 7th of August, by means of a magnifying 

 power of nine diameters, a variation of the position of the air 

 lines with regard to those of the spectrum of Venus was read- 

 ily detected ; the lines in the latter spectrum appeared slight- 

 ly displaced toward the violet, corresponding to the not in- 

 considerable velocity with which Venus, at the time of the 

 observation, was moving toward our earth. The difference 

 between the spectrum of Venus and that of the sun seems to 

 be, essentially, that many of the lines appear stronger than 

 in the solar spectrum. The sodium lines are remarkably dis- 

 tinct, and, under a high magnifying power, look broad and 

 swollen, this being most striking with the one situated near- 

 est the blue. This remarkable widening of the sodium lines 

 can not have been produced by our atmosphere, since in 

 April Mercury was much nearer the horizon than Venus, and 

 yet showed the sodium lines very faint and delicate. It is 

 therefore unquestionable that this variation is due to the at- 

 mosphere of Venus. The magnesium lines also appear to be 

 more distinct than in the solar spectrum, and the spectrum 

 differs from that of Mercury in showing the blue and violet 

 very distinct, while the red is very faint. 



Mars was observed on the 28th of February and the 8th of 

 April. About twenty of the principal lines of the solar spec- 

 trum were observed in the spectrum of this planet. It dif- 

 fered from the solar spectrum in having a remarkably dark 

 band in the red, with a wave length of 695.2 millionths of a 

 millimeter. 



The spectrum of Jupiter was found quite to resemble that 

 of the solar spectrum, about thirty lines being determinable 

 by measurement. Some dark lines visible in the red were 

 ascribed to the very powerful absorption of the atmosphere 

 of Jupiter, and are similar to the dark bands seen in the solar 

 spectrum when the sun is near the horizon, and supposed to 

 be produced by absorption in our atmosphere. 



The spectrum of Uranus was the most remarkable of all, 

 and was characterized by being traversed by peculiar absorp- 

 tion bands. The middle of a dark band corresponds very 



