94: CORRELATION OF PHYSICAL FORCES. 



But, further than this, in the case of certain elementary 

 gases a permanent change is effected by the electrical dis- 

 charge. Thus, oxygen submitted to the discharge is par- 

 tially changed into the substance now considered to be an al- 

 lotropic condition of oxygen ; and there is reason to believe 

 that when the change takes place, there is a definite polar 

 condition of the gas, and that definite portions of it are affected 

 that in a certain sense one portion of the oxygen bears 

 temporarily to the other the relation which hydrogen ordina- 

 rily does to oxygen. 



If the discharge be passed through the vapour of phos- 

 phorus in the vacuum of a good air-pump, a deposit of allotro- 

 pic phosphorus soon coats the interior of the receiver, show- 

 ing an analogous change to that produced in oxygen ; and in 

 this case a series of transverse bands or stratifications appears 

 in the discharge, showing a most striking alteration in its 

 physical character, dependent on the medium across which it is 

 transmitted. These effects were first observed by me in 

 the year 1852. They have since been much examined by 

 continental philosophers, and much extended by Mr. Gassiot ; 

 but no satisfactory rationale of them has yet been given. 



There are many gases which either do not show any per- 

 manent change, or (which is more probably the case) the 

 changes produced in them by the electrical discharge have 

 not yet been detected. Even with these gases, however, the 

 difference of colour, of length, or of the different position of 

 a certain dark space or spaces which appear in the discharge, 

 show that the discharge differs for different media. We nev- 

 er find that the discharge has itself added to or subtracted 

 from the total weight of the substances acted on : we find no 

 evidence of a fluid but the visible phenomena themselves ; 

 and those we may account for by the change which takes 

 place in the matter affected. 



I have here, as elsewhere, used words of common accep- 

 tation, such as ' matter affected by the discharge,' &c., though 



