with Disks of Ebonite. 353 



property which I have not found mentioned of the same 

 apparatus with glass disks : it also develops electricity when 

 the disk is rotating in the direction of the card points. I call 

 this direction (which is just the contrary of the usual motion) 

 abnormal. 



When during some time energetic discharges have occurred, 

 and the diametral conductor is removed from its position, so 

 as to -occupy a position as much on the left of the vertical as 

 before on the right (it has then no armatures before its points), 

 again a series of sparks appear between the horizontal con- 

 ductors when the disks are rotating in the opposite direction 

 to their former one ; even sparks of a length of 5 centims. 

 may then be obtained. The condensers are not necessary; 

 and the same fact is observed with the double electromachines. 

 I believe that the cause of it must be ascribed to the electricity 

 which remains on the armatures, as these are perfectly insulated, 

 and therefore the machine acts as an electrophorus machine. 

 The action is not increasing ; it is rather slowly diminishing. 

 I observed in this case also the singular fact that when the 

 diametral conductor occupies the described position, but the 

 disks are rotating in the usual way (against the card points), 

 the sparks cease to pass between the horizontal conductors ; 

 but often, in the same horizontal conductor, half the points 

 become positively, and the other half negatively electrified, 

 which is evident from their luminous appearance in the dark. 



Action of the electricity on flames. — When trying to dis- 

 charge the ebonite machine by approaching a lighted candle 

 near the disks, I observed a remarkable influence exerted by 

 the accumulated electricity on the shape of the flames. Near 

 the paper armature charged with positive electricity (from 

 whose points negative electricity is escaping) the flame is 

 repelled strongly, and retreats from the disk; near the 

 negative armature it is attracted, and ends in a sharp point. 

 The same is seen with a gas-flame ; and I even succeeded in 

 substituting for the diametral conductor a so-called flame con- 

 ductor, which consists of a wooden rod, whereon no points are 

 fixed, but small glass tubes connected with the gas-pipes of 

 the laboratory. A set of flames is in this way produced be- 

 fore the rotating disk, which, by their forms, denote its posi- 

 tive and negative conditions. 



The explanation of this experiment may be founded on the 

 fact, not very generally known (mentioned by Biess), that 

 when a substance is burnt electricity is generated ; and in the 

 case of carbon being present, the ascending carbonic acid is 

 positively electrified. 



We may conclude from the foregoing statements : — 

 Phil, Mag. S. 5. Vol. 1, No. 5. May 1876. 2 B 



