Page:A history of the theories of aether and electricity. Whittacker E.T. (1910).pdf/356

It is possible that hollow vortices are better adapted than ordinary vortex-filaments for the construction of models of the aether. Such, at any rate, was the opinion of Thomson (Kelvin) in his later years.^[1] The analytical difficulties of the subject are formidable, and progress is consequently slow; but among the many mechanical schemes which have been devised to represent, electrical and optical phenomena, none possesses greater interest than that which pictures the aether as a vortex-sponge.

1. Proc. Roy. Iris. Acad., November 30, 1889: Kelvin's Math. and Phys. Papers, iv, p. 202. "Rotational vortex-cores," he wrote, "must be absolutely discarded; and we must have nothing but irrotational revolution and vacuous cores."