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[Feb. 21, 



thin, are translucent has long presented a clifSculty, -which is only par- 

 tially overcome bj' the assumption, that "the structure is not infinitely 

 fine-grained, with respect to the size of the light waves." It may not 

 be too much to suppose that these new waves are comparable in size 

 with the molecules, or even the atoms, of matter. 



The theory of Prof. Roatgen, already referred to, that the new 

 energj" is longitudinal ether-wave motion, surely must not be ignored, 

 especially as it seems to be supported, among others, by the dis- 

 tinguished mathematical physicist, Prof. Boltzmann, of Vienna. There 

 are difficulties in supposing the ether to be compressible, yet it must 

 assume the etfects of compressibility, if it is to transmit a periodic dis- 

 turbance with finite speed. 



Rontgen's own theory seems well supported by Q. Jaumann (Wiede- 

 mann's Annalen, January, 1896), who has shown in a recent article 

 that by a little change in Maxwell's equations, to satisfy the conditions 

 of high rarefaction, which is met with in a Crookes tube, longitudinal 

 ether waves are possible, which would possess many of the properties 

 of the new rays. 



That the new energy does not consist of cathode rays alone, seems to 

 be proved by the remarkable experiment of J. J. Thomson, who placed 

 a protected plate inside the vacuum tube, exposed to the direct cathode 

 stream, and got no result (Lodge, Electrician, Vol. xxxvi, p. 473). 

 The same experimenter has suggested an eificient and quick way of de- 

 tecting the presence of Routgen rays. An insulated metal plate elec- 

 trically charged, either positivelj^ or negativelj', quickly loses its charge 

 when in the presence of the rays. This occurs even when the plate is 

 entirely embedded in the best insulators. It follows, then, that all sub- 

 stances become electrical conductors, when under the influence of the 

 Rontgen discharge. 



Should the longitudinal ether-wave theory be demonstrated to be the 

 true one. Prof. Rontgen's discovery would be the greatest of the age, 

 and will open up a vast new field for experimental research, and will 

 likely lead to more definite views concerning the nature of the luminif- 

 erous ether. 



Soon after the announcement of this wonderful discovery, we began 

 to experiment in the Physical Laboratory of the University of Pennsyl- 

 vania, at first rather skeptically and quite in the dark as to the exact 

 method of procedure. As the earlier statements implied the necessity of 

 two induction coils, the primary of one connected to the secondary of 

 the other, we were somewhat embarrassed as we did not have two that 

 could be efficiently joined in that way. To show the importance at- 

 tached to this point by early imitators of Rontgen abroad, let me quote 

 a statement by A. A. C. Swinton, who, I am told, was the first in Eng- 

 land to repeat some of Rontgen's experiments. He says (Nature, Vol. 

 liii, p. 377), "So far as our own experiments go, it appears that, at any 

 rate, without very long exposures, a sutticieutly active excitation of the 



