Intelligence and Miscellaneous Articles. 537 



lights by a machine which originally supported only eight. The 

 results in the imperfect vacuum of an air-pump might yet have 

 been in part foreseen ; and they are very curious, as you will see, 

 and as I have just observed with the cooperation of one of my 

 pupils, M. Gr. Maneuvrier. 



Taking an electric egg, I placed in it, face to face, two carbons 

 of 15 centim. length, 4 millim. diameter, separated by an interval 

 of 4 millim. When the exhaustion reached about 12 millim. the 

 light began to spirt out spontaneously, not in the form of a bril- 

 liant arc confined between the points, but starting from all parts of 

 the carbons, with the ordinary appearance of the emanations in 

 Greissler's tubes. Each of them showed, at the same time, the 

 appearances which, with the induction-coil, characterize the two 

 poles — that is to say, the blue aureole enveloping the surface of the 

 two cylinders, which belongs to the negative pole, and, besides, the 

 paler stratified light due to the positive pole. It shot forth normal 

 to the outline of the carbons ; and the whole balloon was filled with 

 fight. The experiment is one of the most beautiful to be seen. 



Thus the two currents contribute each an equal share to the pro- 

 duction of the phenomenon, which is that of the Geissler tubes, 

 but which assumes an incomparable splendour because of the con- 

 siderable quantity of electricity that passes and rapidly modifies 

 the observed appearances. In fact the carbons become heated, 

 redden, and arrive at a pale whiteness, not only at their extremity, 

 but throughout their length ; they are then rapidly volatilized by 

 the combined effect of the heating and the currents. "Whatever 

 may be the cause of this volatilization, it is certain that a carbona- 

 ceous material is diffused in the state of vapour. The balloon 

 becomes filled with a blue gas very similar to iodine vapour, which 

 deepens more and more in colour to indigo. After this the vapours 

 condense abundantly upon the sides of the balloon, which become 

 opaque ; and this terminates the experiment. The deposit collected 

 resembles finely divided carbon, and dissolves with effervescence 

 and incandescence in nitric acid. Is it pure carbon, or a hydro- 

 genated compound of carbon ? That is a question which I reserve 

 for ulterior examination. 



To avoid this forced termination of the experiment, I have 

 replaced each carbon by two equal bundles of crayons fitted to the 

 two rheophores, and diverging in the direction of the generatrices 

 of two cones with their bases opposite. In this case the currents 

 divide into a great number of emanations less intense than the 

 single one ; all the carbons become luminous at once ; and the more 

 numerous they are, the less heated do they become. There is 

 almost no volatilization ; and the effect is prolonged as much as one 

 pleases. 



I have replaced the carbons by copper rods of 3 millim. diameter 

 and diverging from the rheophore. The same effect is produced 

 with still greater splendour. If the current is too intense, the 

 copper melts. It is always in part volatilized, and is deposited in 

 a thin coat upon the balloon. It is evident that the experiment 



