M. Matteucci on the Electricity of Flame. 401 



of alcohol or of hydrogen gas, and probably in all flames, an 

 electric current, the direction of which current in the flame itself 

 is from the portion called by chemists reductive to that called 

 oxidizing ; in other words, the current of the flame is directed from 

 the metallic plate which is in contact with hydrogen or vapour 

 of alcohol, to that which is in contact with oxygen or atmospheric 

 air. You have clearly proved that this current does not depend 

 on the difference of temperature between the two platinum wires 

 placed in the flame, for it is obtained when the wire surrounded 

 by oxygen is held above the flame so as to be less heated than 

 the other. It may be added, that the current obtained by 

 touching directly the greater and the less heated platinum, would 

 only occasion a deflection of a few degrees, instead of which, in 

 operating with the flame, we have a deflection of 40 or 50 degrees 

 in an opposite direction. The currents obtained by employing 

 plates of platinum are much stronger than when wires are used, 

 and the best arrangement is that of holding one of th^ platinum 

 plates so as partly to envelope the flame, while the other is placed 

 in its centre. I have obtained similar results, though the currents 

 have been rather weaker, with copper or iron wires, and from 

 the state of these wires we can judge more distinctly of the 

 portion of the flame which contains hydrogen, and of the external 

 part where oxygen predominates. 



As to the explanation of the production of electricity in flame, 

 I do not for a moment hesitate to consider the case as identical 

 with that by which I think I have explained M. Pouillet^s old 

 experiment and secondary polarities, which formed your start- 

 ing-point in your beautiful discovery of the gas battery ; it is 

 that of an electrical current developed between two metallic 

 plates, and principally between two plates of platinum when 

 plunged in water, being or having been in separate contact, the 

 one with hydrogen, the other with oxygen gas. You are aware 

 that, in the case of flame, I have supposed that these two gases 

 were separated by a stratum of steam. It is known that the 

 electrostatic signs of flame accord perfectly with those obtained 

 with the galvanometer, as well also as with those from the gas 

 battery. 



Before coming to the experiment, which seems to me to leave 

 no doubt as to this interpretation of the electrical phsenomena 

 of flame, allow me to describe some experiments on electrical 

 currents, obtained with platinum wires attached to the extre- 

 mities of the wires of the galvanometer, and immersed in distilled 

 water. I take a platinum wire 3 or 4 metres in length ; after 

 having left this wire for some hours in a mixture of nitric and 

 hydrochloric acids, I wash it repeatedly in hot water. I then 

 cut this wire in two equal parts, and join each half to one of the 

 extremities of the galvanometer which I have already described. 



