1893.] President's Address. 385 



collection, with interesting and ample recognition of its importance 

 in relation to his own work. 



In connexion with the practical development of magnetic waves, 

 you will, I am sure, be pleased if I call your attention to two papers 

 by Professor G. F. Fitzgerald, which I heard myself at the meeting of 

 the British Association at Southport, in 1883. One of them is entitled 

 " On a Method of Producing Electromagnetic Disturbances of com- 

 paratively Short Wave-lengths." The paper itself is not long, and I 

 shall read it to you in full, from the ' Report of the British Asso- 

 ciation,' 1883 : " This is by utilising the alternating currents pro- 

 duced when an accumulator is discharged through a small resistance. 

 It is possible to produce waves of as little as 2 metres wave-length, 

 or even less." This was a brilliant and useful suggestion. Hertz, 

 not knowing of it, used the method ; and, making as little as possible 

 of the " accumulator," got waves of as little as 24 cm. wave-length in 

 many of his fundamental experiments. The title alone of Fitzgerald's 

 other paper, " On the Energy Lost by Radiation from Alternating 

 Currents," is in itself a valuable lesson in the electromagnetic theory 

 of light, or the undulatory theory of magnetic disturbance. It is 

 interesting to compare it with the title of Hertz's eleventh paper, 

 "Electric Radiation"; but I cannot refer to this paper without 

 expressing the admiration and delight with which I see the words 

 "rectilinear propagation," "polarisation," "reflection," "refraction," 

 appearing in it as sub-titles. 



During the 56 years which have passed since Faraday first 

 offended physical mathematicians with his curved lines of force, 

 many workers and many thinkers have helped to build up the nine- 

 teenth century school of plenum ; one ether for light, heat, electricity, 

 magnetism ; and the German and English volumes containing Hertz's 

 electrical papers, given to the world in the last decade of the century, 

 will be a permanent monument of the splendid consummation now 

 realised. 



But, splendid as this consummation is, we must not fold our hands 

 and think or say there are no more worlds to conquer for electrical 

 science. We do know something now of magnetic waves. We know 

 that they exist in nature and that they are in perfect accord with 

 Maxwell's beautiful theory. But this theory teaches us nothing of 

 the actual motions of matter constituting a magnetic wave. Some 

 definite motion of matter perpendicular to the lines of alternating 

 magnetic force in the waves and to the direction of propagation of 

 the action through space, there must be ; and it seems almost satis- 

 factory as a hypothesis to suppose that it is chiefly a motion of ether 

 with a comparatively small but not inconsiderable loading by fringes 

 of ponderable molecules carried with it. This makes Maxwell's " elec- 

 tric displacement " simply a to-and-f ro motion of ether across the line 



