CHAPTER IX. 



ELECTRIC OSCILLATIONS AND ELECTRIC WAVES. 



136. Mechanical conceptions of the magnetic and electric fields.* 

 The foregoing chapters are devoted to the discussion of the 

 phenomena of the electric current and the phenomena exhibited by 

 electrically charged bodies. The phenomena of electric oscilla- 

 tions and especially the phenomena of electric waves have not 

 as yet been touched upon. It is usual to treat these phenomena 

 on the basis of the differential equations of the electro-magnetic 

 field, but it is needless to say that this mode of treatment cannot 

 be followed in an elementary text. The most satisfactory ele- 

 mentary treatment of electric oscillations and electric waves is to 

 develop the mechanical conceptions of the magnetic and electric 

 fields and thus arrive at a rational insight into electro-magnetic 

 phenomena. This method is followed in this chapter. 



Maxwell was the first to work out mechanical conceptions of 

 magnetic and electric fields, and Maxwell's conceptions are used 

 in the present chapter f although certain inconsistencies arise in 

 the attempt to extend these conceptions to three dimensions. 



* Sir Oliver Lodge's Modern Views of Electricity is perhaps the best elementary 

 treatise on this subject. This book is now (1908) being rewritten. 



tThe most complete mechanical conception of the electro-magnetic field is that 

 which is based upon Lord Kelvin's gyrostatic model of the ether. This gyrostatic 

 model of the ether is a mechanical structure which is capable of reproducing most of 

 the known phenomena of electricity and magnetism and of light. See JEther and 

 Matter, by Joseph Larmor, Appendix E, Cambridge, 1900. Lord Kelvin's gyrostatic 

 model of the ether has led to a hydrodynamic conception of the ether, due chiefly to 

 Larmor, in which the ether is assumed to be a perfect fluid which is endowed with 

 the necessary elastic properties by an indefinitely fine grained whirling motion. On 

 the basis of Lord Kelvin's gyrostatic conception of the ether and also on the basis of 

 Larmor' s turbulent ether, the magnetic field is thought to consist of a simple flow of 

 the ether along the lines of force of the magnetic field. This conception of the 

 magnetic field is very different from the conception which is outlined in this text and 

 which is based upon Maxwell's conception of the ether. 



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