660 Prof. Taylor Jones and Mr. Roberts on Musical 



system were sounded, would the period o£ vibration be Tj -f-T 3 ? 

 In the case where the gases 1 and 2 become identical we 

 know that the period o£ the combined system is obtained 

 correctly by adding together the corresponding values of 

 r l and t 2 . I do not know of the general case with two unlike 

 gases having been tried. In the radiational case of NaCl, 

 KC1, KBr and KI just considered, we have found that the 

 periods of the two atoms in each compound have to be added 

 together to give the period for the molecule. Now an exactly 

 similar result was brought out in my paper on "A New 

 Periodic Property of the Elements " (Phil. Mag. [5] xxx.) 

 with a correction in " A Kinetic Theory of Solids " (ibid. 

 xxxii.), and further consideration in " The Cause of the 

 Structure of Spectra " (ibid. [6] ii.). It was shown that the 

 atoms of the metallic elements and the molecules of their com- 

 pounds at their melting-points have characteristic oscillations. 

 The period of oscillation for a compound molecule like NaCl is 

 shown to be obtainable as the sum of a period for Na and a period 

 for CI. This fact supports the assumption made above that in 

 calculating the mechanical period of vibration and wave- 

 length of NaCl we are to add the periods and lengths for Na 

 and CI. Moreover it is interesting to recall that the kine- 

 matical explanation which I have offered for the origin of 

 Balmer's formula leads to the consideration of the period of 

 each spectral line as the sum of two periods. From the 

 calculations given above it appears that ordinary harmonic 

 relations are to be expected amongst the wavs-lengths of a 

 substance in the extreme infra-red. 

 Melbourne, June 1910. 



LXXI. Musical Arc Oscillations in Coupled Circuits. By 

 E. Taylor Jones, D.Sc, Professor of Physics in the 

 University College of No7*th Wales, and David E.Roberts, 

 B.Sc, Isaac Roberts Student of the University College of 

 North Wales, Bangor*. 



[Plate XIII.] 



IN a former communication t a number of photographs 

 . were reproduced showing the variation of potential at 

 the terminals of the secondary of a pair of coupled circuits 

 when the two oscillations of the system are simultaneously 

 maintained by a musical arc connected to the primary. In 



* Communicated by the Authors. 



f E. T. Jones and Morris Owen, Phil. Mag. November 1909, p. 713. 



