702 



Prof. J. E. Ives on the Absorption of 





It is scarcely necessary to remark that the law of flow 

 along the stream-lines is entirely different from that with 

 which we are familiar in the flow of incompressible liquids. 

 In the latter case the motion is rapid at any place where 

 neighbouring stream-lines approach one another closely. 

 Here, on the contrary, the motion is exceptionally slow at 

 such a place. 



LXXII. On the Absorption of Short Electric Waves by Air 

 and Water-Vapour. By James E. Ives, Ph.D., Associate 

 Professor of Physics in the University of Cincinnati *. 



IT is well known that Wireless Telegraph signals can be 

 sent farther at night than in the day. One of the 

 suggestions that has been made to explain this fact is, that 

 the air may absorb more of the energy of the waves during 

 the daytime than it does during the night ; the absorption of 

 the waves being supposed to be due to the ions produced, 

 either in the lower or in the upper laj^ers of the atmosphere, 

 by the action of sunlight. 



It was this fact and the suggested explanation of it which 

 led to the research described in this paper. 



Moserj, Thomson J, Tesla §, Remington ||, Ebert and 

 Wiedemann IF, and Wiedemann and Schmidt**, have investi- 

 gated the ionization of a gas at low pressures by a powerful 

 alternating electric field. They have shown that gases when 

 ionized in this manner, and especially when glowing, become 

 highly conducting, and indeed to such an extent that when 

 placed between the source of the oscillating field and some 

 other conducting body, they shield the latter from electrical 

 disturbances. 



Lecher tt* hy using a double-walled glass vessel like a 

 Bunsen calorimeter, placing a coil of wire within the inner 

 tube and winding four turns of wire on the outer tube, has 

 shown that if high frequency oscillations are set up in the 

 outer coil, and the pressure of the air between the tw r o tubes 

 is reduced, the rariried air will absorb a large part of the 

 energy of the outer coil. He found that the absorption was 



* Communicated b} r the Author. 



f Comptes Rendus, ex. p. 397 (1890). 



X Phil. Mag. xxxii. pp. 321-336, 445-464 (1891). 



§ Elect. Eng. xii. pp. 14, 15 (1891). 



|| Phil. Mag. xxxv. pp. 506-525 (1893). 



f Ann. Phys. xlix. pp. 32-49 (1893). 

 ** Ann. Phys. lxii. pp. 460-467, 468-473 (1897). 

 tt Phys. Zcitsclu; iv. pp. 32-38 (1902). 



