498 



Profs. Liveing and Dewar. 



[June 10, 



■of a character quite different from that at the less refrangible end. 

 The most remarkable part of this spectrum is a long series of closely 

 set strong lines, filling the region between the solar lines R and S, 

 and ending abruptly with two strong lines a little beyond S. These 

 are lines of various intensities, not regularly arranged so as to give 

 shaded bands like those in the less refrangible part of the spectrum. 

 Beyond these lines there is another large group of lines, not so strong 

 or so closely set, but sharp and well defined. It will be a work of 

 time to examine in detail this very striking and peculiar spectrum ; 

 at present we can only indicate its general character. We are not yet 

 sure whether it is produced by pure hydrocarbons, or may not be due 

 to impurities such as sulphur in the coal gas.* 



Spark Discharge in Carbon Tetrachloride. 



We have conducted the experiments with carbon tetrachloride with 

 great care, and numerous repetitions on account of the prominence 

 given to an experiment with this compound by Mr. Lockyer in a recent 

 " Note on the Spectrum of Carbon, " communicated to the Society, and 

 because our results in every case differ from those which he obtained. 



The form of sparking tube employed was similar to that used by 

 Salet, and is shown in the annexed diagram, fig. 4. This was attached 



b)y thick rubber tubing to a straight glass tube of which one half, 

 about 6 inches long, was filled with phosphoric anhydride, and the 

 other half with small fragments of soda-lime to prevent any chlorine 

 from the decomposition of the tetrachloride by the spark from reaching 

 the pump. The pump was connected by rubber tubing to that end of 

 the tube which contained soda-lime. The tetrachloride used had been 

 prepared in our own laboratory from carbon disulphide, and frac- 

 tionated until it had a constant boiling point of 77° C. Sufficient 

 of it was introduced into the sparking tube to fill nearly one quarter 

 of the bulb at the end, and the whole interior of the tube thoroughly 

 wetted with it in order to facilitate the removal of the last traces of air. 



* Since this passage was written we have found reason to belieye that this re- 

 markable spectrum is due not to any carbon compound, but to water. As this takes 

 it beyond the scope of the present paper, we purpose dealing with it hereafter in a 

 separate communication. June 8, 1880. 



