Stoney — On Texture in Media, etc. 401 



very much strengthened by the discovery made by Helmholtz 

 about a quarter of a century ago, of the persistence and dynami- 

 cal behaviour of vortex rings and other vortex filaments in a 

 perfect incompressible fluid, and by the investigations to which 

 this discovery has led. 



One result of these investigations has been to suggest to Sir 

 William Thomson that the chemical atoms of which ponderable 

 matter consists may be simply vortex tangles in such a medium ; 

 and to suggest to Professor FitzGerald that the luminiferous ether 

 may be a medium of this kind permeated by straight vortex fila- 

 ments in all directions. Investigations are being actively pushed 

 forward with a view to ascertaining how far these suppositions 

 can be corroborated. Other hypotheses which may be classed with 

 these have been advanced by Professor Hicks and others, but I 

 select Professor FitzGerald's and Sir William Thomson's, both 

 because they seem, in our present imperfect state of information, 

 the best of their class, and in order to give defmiteness to what 

 further I have to say. 



Let us then imagine this room to be permeated by three sys- 

 tems of wires. Let the first be a set of vertical wires from the 

 ceiling to the floor in rows parallel to the walls, and at intervals 

 from one another of one inch. Let a similar system cross the 

 room from side to side, passing midway between the wires of the 

 first set : and let a third system of wires run from end to end of 

 the room threading their way along the middle of the clear pas- 

 sages that lie between the wires of the other two systems. Let 

 these wires represent straight vortex filaments in a uniform in- 

 compressible medium devoid of stress resisting change of form, and 

 let the alternate vortex filaments of each row rotate in the same 

 direction, while the intermediate ones rotate in the opposite direc- 

 tion, but let the vortex filaments be in other respects similar. 



Such would be the simplest case of a medium of the kind that 

 Professor FitzGerald has conceived, (o) Let us next imagine the 

 whole space within the room to be divided into large blocks of a 

 cubic yard in size. One of these blocks will include a great 

 number of the vortex filaments, and all the large blocks will 

 closely resemble one another ; insomuch that if an undulation 



(o) Nature, May, 1889, vol. xl., p. 32. 



