178 Mr. J. N. Lockyer. On the Classification [Jan. 10, 



Jane 10th), Copeland recorded a bright line at 426'1, and it was also 

 possibly shown in Huggins's photograph of the spectrum of the same 

 comet taken on May 31st, its wave-length being given as 425'3. On 

 each of these occasions, other evidences of carbon were entirely absent, 

 and the bright lines present in the spectrum gave indications of 

 a relatively high temperature. 



There are several reasons why the carbon line spectrum has not 

 been recorded a greater number of times. First, very few comets 

 approach sufficiently near the sun to attain the necessary temperature. 

 Second, the principal line is in a part of the spectrum which is very 

 difficult to observe. Even in the Great Comet of 1882, which was 

 very bright, the observations did not go beyond 465. 



This conclusion cannot be regarded as final until careful differential 

 observations of nucleus, envelopes, and jets are made. At present 

 the exact part of the comet the spectrum of which is described is 

 generally not stated, and there is evidence that, up to the highest 

 temperature produced by collisions, carbon in some form is liberated 

 from the meteorites composing the cometary swarm. 



The Perihelion Conditions of the Great Comet of 1882. 



As the perihelion distances are different in different comets, we 

 must expect the effects to be more decided in some cases than others. 

 The most remarkable case since the beginning of spectroscopic inquiry 

 was afforded by the Great Comet of 1882, most admirably observed 

 by Copeland. 



It is found that many of the lines which have been observed at 

 perihelion are coincident with lines seen in experiments with meteo- 

 rites, while the low temperature lines of magnesium are absent. In 

 the Great Comet of 1882, 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 6 which might be due to 

 magnesium, or to a remnant of the carbon fluting. There were also 

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

 yet been determined. 



The following is a complete list of the lines recorded by Copeland 

 and Lohse* on the day after perihelion passage. The origins of the 

 lines which my observations have suggested are also given. 



' Copernicus,' vol. 2, p. 239 



