WAVE-LENGTH ON STRAIGHT CONDUCTOR. 



255 



For these and the interferometer measurements, the 

 oscillator, sparking in paraffin, was placed at the focus of 

 a cylindrical parabolic mirror, the focal length being an 

 odd multiple of a quarter of the wave-length to be expected. 

 Experiments have been made with mirrors whose focal 

 lengths were calculated from the lengths of the oscillators 

 on the basis of both Abraham's and Macdonald's theories. 

 Ives' conclusion that the focal length of the oscillator mirror 

 has a negligible effect on the wave-length has been verified. 



The various values which have been found are set out in 

 the following table, together with the names of the experi- 

 menters who carried out the considerable practical work 

 involved in the determinations. To make the evidence 

 complete, I have included the results of Ives' measurements. 

 The other measures, previously mentioned, are not given 

 in the table as the earlier experiments are open to the 

 criticism that the influence of the receivers was not entirely 

 eliminated. Ives' use of a very high resistance in the 

 receiver circuit quite obviates an error of this kind. In 

 the experiments in this laboratory, coherers of very dis- 



Experimenters. 



Length of 

 Oscillator 



A 



observed. 



A 



calculated 



k 



observ'd 



k 



calcul'd. 



Experi- 

 mental 

 Method. 



Number 

 of nodes 

 deter- 

 mined. 



Approxi- 

 mate dis- 

 tance from 

 plane 

 mirror. 



"*Ives 



4-93 



10-42 



10-12 



211 



2-05 



Interfero- 

 meter. 









7-49 



15-24 



15-30 



2-03 



2-04 



:j 









9-85 



19-86 



20-06 



2-02 



2-04 



)i 







T£ooth&Tidd y 



5-06 



1040 



10-30 



2-06 



2-06 



j> 



3 





»? 



j> 



10-54 



ji 



2-08 



>» 



Stationary 

 Waves. 



4 



100A. 



j) 



j< 



10-46 



jj 



2-07 



j> 



,, 



4 



jj 



)) 



5» 



10-40 



') 



2-06 



5* 



JJ 



3 



5A. 



}? 



18-84 



38-47 



38-38 



2-05 



2-03 



JJ 



11 



20A. 



% Anderson and 



!) 



38-00 



?j 



2-01 



5» 



J> 



5 



5A. 



Hcarr 



















Ives, loc. cit.. f E. H. Booth, H. P. Tiddy. + E. C. Anderson, J.H. A. Scarr 



