hy Chemical Action. 109 



sun rays, I shall return to the consideration of this spectrum 

 and to the nature of fixed lines presently ; here only making 

 the remark, that the burning of cyanogen, both as respects 

 the colour of the light and the occurrence of fixed lines, is a 

 direct consequence of the principle I am establishing. 



The unassisted eye detects two well-marked regions in the 

 cyanogen flame; a greenish-gray stratum on the outside, 

 and a lilac-coloured nucleus within. Decomposed by the 

 prism, a horizontal element of this flame shows that the exte- 

 rior shell contains all the prismatic colours, except perhaps 

 the yellow ; but the green, the blue, and the violet greatly 

 predominate. The interior lilac flame is the source of the 

 bright spectrum with fixed lines just described. 



V. Conlinuation of the same jirinciple in the case 'where com- 

 bustioti is carried on in oxygen gas itistead of atmospheric air. 



If the principle that high refrangibility is connected with 

 intense chemical action be true, it must hold good when the 

 nature of the atmosphere in which the burning is carried for- 

 ward is changed. If instead of being the common air it is 

 oxygen gas, we ought to be able to foresee the result. Car- 

 bonic oxide, when made to burn in that gas, should not change 

 its tint ; because if the air can carry on the process to its 

 maximum effect, oxygen can do no more. But the result 

 should be just the reverse with cyanogen, which, if made to 

 burn in oxygen, should be capable of emitting rays of higher 

 refrangibility. 



Foreseeing this result, I proceeded to submit the two gases 

 to the test of experiment, and first arranged the carbonic oxide 

 that its spectrum might be examined in the telescope as already 

 described ; then causing a clean bell-jar full of oxygen to be 

 inverted over it, the flame diminished somewhat in size, emit- 

 ted a slight crackling sound, but retained its colour unchanged. 

 Its spectrum appeared precisely the same, both as respects 

 extent and the distribution of colour, whether the burning 

 took place in oxygen gas or in the atmospheric air. 



If cyanogen be made to burn in oxygen, we should expect 

 that it would lose to a great extent its characteristic lilac tint, 

 and emit a whiter light. It was therefore very interesting to 

 find, that the moment the flame was immersed in oxygen it 

 lost much of its pinkish colour, and became of a dazzling 

 brilliancy: and on examination through the telescope, though 

 all the colours had increased in brightness, the most remark- 

 able eflcct took place among the extreme refrangible rays. 

 Far out of the limits of the ordinary spectrum, a ray of great 



