Intelligence and Miscellaneous Articles. 15? 



in a peculiar property of" the alternating currents that the reason of 

 the differential current must be sought. 



Each of the two systems of currents stores up, at the instant of 

 its commencement, a certain sum of energy, which is set free when 

 it ceases, and is manifested by a contrary current, or, as Edlund 

 says, by an inverse electromotive force. Thus a first current ^-*-, 

 initially very feeble, gradually increases, and, when it ceases, gives 

 rise to an inverse reaction ■*-, which adds itself to the current ■*- 

 developed by the machine at the same instant. If, then, one of the 

 systems of current -»■ presents a weaker reaction than the contrary 

 system ■*— , it will be less weakened and more reinforced, and will 

 determine the direction of the differential current. 



Whatever may be the explanation of these facts, it is clear that, 

 once produced by an arc with mercury, the differential current 

 entirely changes the action of the machine, that one of the systems 

 of currents is, if not extinguished, at least considerably weakened, 

 and that the other system is constituted by successive currents of 

 greater intensity and duration. Also every additional electric arc 

 introduced presents the same aspect as that of the batteries — that 

 is to say, greater brightness and heat at the positive pole, with 

 transfer of matter to the negative pole. The machine, previously 

 incapable of decomposing water, becomes capable of decomposing it 

 like a battery with an electromotive force equal to 100 Bunsen 

 pairs ; it can, like the batteries, determine all the chemical actions 

 we will, magnetize soft iron, reduce metals, convey force — in a 

 word, replace a continuous-current machine in its applications. 



There are two types of magneto-electric machines : those of the 

 one kind, derived from the G-ramme system, can give directly cur- 

 rents constant in direction ; the others, like those of Xollet or Meri- 

 tens, can engender only alternating currents : the latter are appli- 

 cable only to the production of light : it has been in vain attempted 

 to employ them for chemical operations by directing the currents 

 with a commutator. It is evident that this commutator might be 

 replaced automatically by one or more arcs formed between a bath 

 of mercury and a carbon point*. It remains to ascertain what are 

 the economical conditions of that transformation. — Comptes Eendus 

 de VAcademie des Sciences, June 19, 1882, pp. 1615-1619. 



ON THE MOTION OF A SPHERICAL ATOM IN AN IDEAL GAS. 

 BY G. LUBECK f- 



The author considers an atom of mass M, moving through a gas 

 at rest, of which the atoms are of mass m. With respect to the 

 impact, he avails himself of the principle of vis viva, of that of the 

 centre of gravity, and, lastly, of the principle that communication 



* These experiments were made at the laboratory of the Sorboime. 

 t Festschrift r7es Fried, - Werd, -Gijmn. Berlin, 1881, pp. 295-312. 



