[ ioo ] 



XII. On the Spectra of Carbon. By W. Marshall Watts, 

 D.Sc.. Physical- Science Master in the Manchester Grammar 

 School*. 



TN a paper published in the Philosophical Magazine for Octo- 

 ber 1869, I showed that carbon, like hydrogen and nitrogen, 

 is capable of giving two or more distinct spectra, and I endea- 

 voured to explain these differences as dependent solely on differ- 

 ences in the temperature to which the carbon-vapour was heated. 

 Leaving the spectrum of the Bessemer flame out of consideration, 

 the following estimations of temperature were given for the car- 

 bon spectra I., IL, and IV. : — 



CII Below 1500° C. 



CI 1500° C. to 10,000° C. 



C IV Above 10,000° C. 



The spectrum No. II. is that obtained by the electric discharge 

 in carbonic oxide or olefiant gas at a few millimetres pressure. 

 The only evidence for the temperature assigned to it was the 

 fact that the electric spark in either carbonic oxide or olefiant 

 gas at the ordinary pressure gives the spectrum No. I., that on 

 increasing the density of the gas the temperature rises, as is 

 shown by the addition of new lines (groups f and 0), but on di- 

 minishing the pressure the spectrum No. I. gives place to spec- 

 trum No. II. The lowest temperature at which the spectrum 

 No. I. is produced having been shown to be about 1500° C, it 

 was concluded that spectrum No. II. belonged to temperatures 

 below 1500° C. 



It appeared probable that more decisive evidence as to the 

 temperature of the discharge in a Geissler's tube might be ob- 

 tained by means of certain sodium- and lithium-lines, which 

 become visible only at a high temperature. If a bead of sodium 

 chlorate be brought into a Bunsen- flame, the spectroscope shows 

 during the final deflagration of the salt, besides the D lines, four 

 other groups of lines, whose wave-lengths are given in Ang- 

 strom's map as follows : — 



Na/3 . . < Kfior f ten-millionths of a millimetre. 

 m ? ' • 1.5150/ 



M . T4982 1 



NaS ' ' l4983i) 



N f6160\ 



l>ae . . ^ 6154 | >> 



* Communicated by the Author. 



a it 



}> 



