254 J. A. POLLOCK. 



More recently several values of the ratio of wave-length 

 to length of conductor, determined from interference 

 experiments, have been given in accounts of measurements 

 of electric waves from linear oscillators of small dimensions. 

 Writing A. = kl, where I is the length of the conductor, 

 Wiliard and Woodman 1 deduce for k the value 2*48; Oole, 2 

 2*52; Blake and Fountain, 3 2*47, and Webb and Woodman, 4 

 2*3. Finally Ives, 5 using a very high resistance receiver 

 with an interferometer arrangement, finds 2*04 as the value 

 of k for certain linear oscillators varying in length from 

 5 to 10 centimetres. 



At the meeting of the British Association in Sydney, in 

 1914, I mentioned that the interference experiments had 

 recently been repeated by students in the Physical Labora- 

 tory of the University, with results completely confirming 

 those of Ives. I now give a summary of the measurements. 



In the interferometer experiments Ives' general arrange- 

 ment has been followed, but a coherer was used as a 

 receiver instead of one involving a thermo-electric junction. 

 At each observation the coherer was isolated during the 

 passage of the waves, being connected to the galvanometer 

 circuit, by moveable conductors working in mercury cups, 

 only after sparking had ceased. A coherer used in this 

 way is unaffected by disturbances not in its immediate 

 neighbourhood. 



The positions of the nodes of the stationary wave system, 

 formed by the reflection of an incident beam at a plane zinc 

 mirror, have also been determined with the same coherer 

 arrangement. The results exactly agree with those found 

 with the interferometer. 



1 Wiliard and Woodman, Phys. Rev., 18, p. 1, 1904. 



2 Cole, Phys. Rev., 20, p. 268, 1905. 



3 Blake and Fountain, Phys. Rev., 23, p. 256, 1906. 



4 Webb and Woodman, Phys. Rev., 29, p. 89, 1909. 



5 Ives, Phys. Rev., 30, p. 199, 1910 ; 31, p. 185, 1910. 



