OF GASES, ETC. 41 



to the electric light, though it is probable such 

 does exist. 



In the above experiment, when other gases are 

 mixed with the rarefied oxygen, the effect is some- 

 what increased, probably because a certain amount 

 of chemical action is set up. 



Our readers know, that by passing the dis- 

 charges of a RuhmkorfFs induction apparatus 

 through a glass globe in which the air has been 

 highly rarefied, a beautiful luminous phenomenon 

 occurs and persists as long as the induction ap- 

 paratus continues to work. When the vapour of 

 some volatile substance, such as alcohol, essence 

 of turpentine, naphtha, bichloride of tin, etc., is 

 mixed with the air in the glass globe, and a va- 

 cuum then produced by the pneumatic machine, 

 the luminous phenomenon is still more beautiful. 

 The light forms a series of concentric arches 

 separated by dark stratifications ; its colour and 

 form remind us of the Aurora Borealis ; and, in- 

 deed, some have looked upon this experiment as 

 the production of an artificial aurora, the vacuum 

 of the glass globe (which is never a perfect void) 

 representing the rarefied air in the higher regions 

 of the atmosphere, where the Aurora Borealis 

 occurs. 



The light thus produced, to be seen to advan- 

 tage, must be viewed in a dark room, but it is 

 faintly visible in full daylight. 



