84 Mi' Purvis and Miss Homer, The absorption spectra, etc. 



the red end, and that this shift is more marked still for the 

 absorption bands of the solid hydrocarbon. 



Endeavours were also made to observe the absorption spectrum 

 of the vapour of the hydrocarbon. For this purpose a small 

 portion of the solid was placed in a thick hard glass bulb of about 

 50 mm. diameter. The bulb was then exhausted of air and placed 

 in a special apparatus designed to heat the bulb equally in all 

 directions so that the density of the vapour would be the same at 

 every point. The light of an iron arc or of a condensed ii'on spark 

 was used for different observations, but it was found that the 

 hydrocarbon decomposed so rapidly that no results were obtained. 

 The vapour of the hydrocarbon exhibited a most beautiful blue 

 fluorescence, very intense at first but rapidly becoming weaker. 

 The decrease in fluorescence seemed to be proportional to the 

 decomposition of the hydrocarbon, as evidenced by the conversion 

 of the substance to a brownish tarry residue. The decomposition 

 may have been started either by the action of the small amount of 

 air left in the bulb or by the contact action of the heated glass. 



We hope to continue the work on the absorption and fluorescent 

 spectra of the vapour of this and of other hydrocarbons. 



