wUJi the Chemical Constituents of the Solar System. 385 



of such diamonds. Some corroboration of this theory is to be 

 found in the fact that some meteors contain carbon in the form 

 of graphite; and the connexion between meteoric streams and 

 comets seems to be estabhshed. It occurred to me to examine 

 whether the volatiHzed carbon between the points of an electric 

 light gave out this band spectrum. I found it difficult, though 

 not impossible, by the aid of Mr. Ladd, to throw this light 

 upon the screen without the overpowering flood of light from 

 the white-hot points themselves. A more convenient way of 

 examining it was to throw the image of the charcoal points 

 upon the screen in the usual manner, to place my eye in the 

 intermediate blue, and look at the source of light with a direct- 

 vision spectroscope. I thus found that with large battery- 

 power, and the points far removed from one another, there 

 appeared occasionally a band spectrum, but that generally 

 it burst forth as a multiplicity of bright lines. When, how- 

 ever, the spark was made about as feeble as possible, there 

 appeared pretty constantly the three bands closely resembling 

 those observed in carbon compounds and the heads of comets; 

 and a measurement of the brightest portion, the least-refran- 

 gible edge of the middle band, confirmed my belief in their 

 identity*. While, however, it is possible that the light of the 

 heads of comets is due to pure vapour of carbon, there seems to 

 me to be a very serious difficulty in theory. The luminous gas 

 in falling back again to the tail would condense into drops of 

 liquid or solid carbon, which at their first formation must 

 necessarily pour forth a flood of rays of every refrangibility; 

 but this is not the case. It seems to me more probable that 

 the material shining in the heads of comets is of the nature of 

 carbonic oxide, or of those hydrocarbons which we know are 

 occluded in many of the iron meteorites, and which could be 

 easily driven out by any heat, even if they do not form a part 

 of their atmosphere under ordinary circumstances. 



We thus see that the deductions drawn from the theory that 

 the solar system was once a great nebulous mass, are borne 

 out by the chemical phenomena accessible to us ; and this of 

 course affords another argument in favour of the nebular 

 theory itself. 



* After reading my paper, I learnt that Captain Abney had previously 

 made similar observations with the spark of the magneto-electric light. 



Phil. Mag. S. 5. Vol. 4. No. 26. Nov. 1877. 2 C 



