227 



supplied by Mr. Dancer, a jet of oxygen being surrounded by 

 an annular jet of the coal gas. Mr. Dancer has further 

 improved the jet by allowing the oxygen pipe to project 

 beyond the hydrogen, and by not contracting the aperture of 

 the hydrogen pipe. 



Mr. Alfred Fryer exhibited the light which he had 

 explained, and the effect produced was very striking. 



Professor Roscoe read the following communication, by 

 Professor Clifton and himself, entitled, '^ On the Effect of 

 Increased Temperature upon the Nature of the Light Emitted 

 by the Vapour of certain Metals or Metallic Compounds." 



In a letter communicated to the Philosophical 3Iagazine 

 for January last, we stated that in examining, with Steinheil's 

 form of Kirchhoff and Bunsen's apparatus, the spectra pro- 

 duced by passing the induction spark over beads of the 

 chlorides and carbonates of lithium and strontium, we had 

 observed an apparent coincidence between the blue lithium 

 line, which is seen only when the vapour of this metal is 

 intensely heated, and the common blue strontium line called 

 Sr §. Y/e further stated that on investigating the subject 

 more narrowly by the application of several prisms and a 

 magnifying power of 40, we came to the conclusion that the 

 lithium blue line was somewhat more refrangible than the 

 strontium 8, but that two other more refrangible lines were 

 observed to be coincident in both spectra. Having con- 

 structed a much more perfect instrument than we at that 

 time possessed, we are now able to express a definite opinion 

 ou the subject, and beg to lay a short notice of our observa- 

 tions before the Society. Our instrument is in all essential 

 respects similar to the magnificent apparatus employed by 

 Kirchhoff in his recent investigations on the solar spectrum 

 and the spectra of the chemical elements. It consists of a 

 horizontal plane cast iron plate, upon which three of Steinheil's 

 Munich prisms, each having a refracting angle of 60°, are 



