Intelligence and Miscellaneous Articles, 375 



therefore also the self-induction, is independent of the magnetic 

 nature of the substance. In consequence of this, electrical waves 

 of high periods travel in an iron wire with the same velocity 

 as iii one of copper. According to an experiment made by Hertz 

 this, as a fact, is the case. Hertz explains this by the assumption 

 that the magnetism of iron cannot follow such rapid vibrations. 

 According to what is here stated the matter is much simpler : the 

 iron remains free from any magnetic action of these vibrations. 



From the experiments of H. Hertz, it results that the propaga- 

 tion of electrical waves in thin and thick wires takes place with 

 the same velocity. According to the distribution of such waves on 

 the surface of a conductor, it follows that this velocity in a straight 

 conductor is independent, not only of the magnitude, but also of 

 the form of the section. The coefficient of self-induction may be 

 expressed by twice the potential of the electrical charge on itself 

 divided by the square of the quantity. If in calculating the potential 

 of the current we take the formula propounded by Neumann for the 

 potential of two elements of current, this, in a straight conductor in 

 which only parallel elements occur, reduces to the potential of two 

 elements of the statical charge. If now the current-density as well 

 as that of the charge in the surface are divided according to the 

 same law, the same calculation must be made to determine the two 

 potentials. Both are in like manner dependent on the size and 

 shape of the section ; and accordingly the product of the coefficient 

 of induction and the capacity, as well as the velocity of propagation 

 of the waves, are independent of the size and form of the section. 

 The identity in the form of the electrodynamic and electrostatic 

 potential has the consequence that the distribution of the current 

 on such conductors as are parallel, and not connected with each 

 other, may be determined by the rules of electrostatics. Here the 

 potential of a conductor, which is only evoked by the induction of 

 the other, must be called zero. — Wiener Berichte, January 9, ]890. 



ELECTEICAL VIBRATIONS IN RAREFIED AIR WITHOUT 

 ELECTRODES. BY JAMES MOSER. 



Incited by the view of Heaviside and Poynting, that electrical 

 vibrations penetrate into a wire from the surface, and influenced 

 by Hertz's experiments with the wire cage*, the author has used 

 rarefied spaces without electrodes as conductors in which electrical 

 vibrations occur. 



A glass tube which contained a gas of constant rarefaction was 

 surrounded with a wider tube, and the rarefaction varied in this 

 by means of the air-pump. The following results were obtained: — 



(«) At the ordinary atmospheric pressure in the outer tube the 

 inner tube becomes luminous. 



(6) With a sufficient rarefaction of the outer tube the pheno- 

 menon is reversed ; the inner tube becomes dark and the outer one 

 luminous. Here there is obviously a screening action. 



* Wiedemann's Annalen, xxxvii. p. 395. 



