1887.] 



Researches on the Spectra of Meteorites. 



129 



will, I expect, be found to be iron lines when other observations are 

 made of the spectra of meteors. 



The main conclusions from this comparison are then : (1) that the 

 temperature of luminous meteors is higher than that of the Bunsen 

 flame ; (2) that the meteorites which produce the phenomena we are 

 now discussing are hotter than those in the experimental glow taken 

 generally ; and (3) that in both cases flutings of carbon may be seen. 



/3. Comets. 



When the meteorites are strongly heated in a glow-tube, the whole 

 tube when the electric current is passing gives us the spectrum of 

 carbon. 



When a meteor-swarm approaches the sun, the whole region of 

 space occupied by the meteorites, estimated by Professor Newton in 

 the case of Biela's comet to have been thirty miles apart, gives us the 

 same spectrum, and further it is given by at all events part of the tail, 

 which in the comet of 1680 was calculated to be 60,000,000 miles in 

 length. The illumination therefore must be electrical, and possibly 

 connected with the electric repulsion of the vapours away from the 

 sun ; hence it is not dependent wholly upon collisions. 



Passing now from the flutings seen in cometary spectra, it is found 

 that most of the lines which have been observed at perihelion are 

 coincident with lines seen in experiments with meteorites, while the 

 low temperature lines of Mg are absent. In the great comet of 1882, 

 to which particular attention has been given on account of the com- 

 plete record of its spectrum by Copeland,* the lines recorded were 

 the D lines of sodium, the low temperature iron lines at 5268, 5327, 

 -5371, 5790, and 6024, the line seen in the manganese spectrum at 

 the temperature of the bunsen burner at 5395, and a line near b 

 which might be due to magnesium, or to a remnant of the carbon 

 fluting. In addition to these there was a line at 5475, probably due 

 to nickel, the absence of the blue strontium line indicating that it is 

 not likely to be the green line of strontium. There were also four 

 other lines less refrangible than D, the origin of which has not yet 

 been determined. As the comet got further from perihelion the lines 

 gradually died out, those which remained longest being the iron line 

 at 5268 and the line near b. The absence of D before the disappear- 

 ance of all the lines is probably to be accounted for partly by the 

 greater brightness of the continuous spectrum in that region. 



In the comets of 1866-67, when seen away from the sun, the only 

 line seen was the one at 500.f 



* ' Copernicus/ vol. 2, p. 234. 



t " In January, 1866, 1 communicated to the Koyal Society the result of an exami- 

 nation of a small comet visible in the beginning of that year (' Koy. Soc. Proc.,' 

 vol. 15, p. 5). I examined the spectrum of another small and faint comet in May, 



