May 2t, 1896] 



NA TURE 



67 



vacuum tube. The query at once arises, if glass is permeable 

 to these particles in virtue of their relatively great velocity, 

 why is it not permeable (in lesser degree) to tlie same particles 

 moving with smaller velocities ? That it is not, is evident from 

 the fact that vacuum tubes retain their high degree of exhaus- 

 tion unimpaired for years. 



In view of these diliiculties, I would propose a third theory, 

 which may be called the "ether-vortex" theory. 



Let it be supposed that the X-rays are vortices of an inter- 

 molecular medium (provisionally, the ether'). These vortices 

 are produced at the surface of the kathode, by the negative 

 charge, which forces them out from among the molecules of the 

 kathode. 



Let us now apply the tests above mentioned. 



According to this theory, an oscillatory discharge, while it 

 may be just as effective as a series of separate impulses, is not 

 essential to the formation of the vortices. The vortices being 

 forced outwards from the surface of the kathode by the negative 

 charge, the effect of the positive charge at the anode would be 

 to drive them in. Hence their appearance at the kathode alone. 



One of the greatest puzzles connected with the behaviour of 

 the X-rays is the fact that while they can pass almost unimpeded 

 through air at atmospheric pressure (let alone water, glass, wood, 

 flesh, bone, and metals) wZ/ev; once outside the enclosure in which 

 they are produced, they cannot even reach the walls of the 

 enclosure, except there be a very high vacuum within. This 

 problem receives a very natural solution if it be considered that, 

 in order that ether-vortices may result from the electrical 

 impulse, this impulse must be communicated to them ; and must 

 not be dissipated in the interchange of molecular charges which 

 acconijianies, or rather produces, the discharge at moderate or 

 high pressures. 



As exhaustion proceeds there are fewer molecules present to 

 effect this discharge with sufficient rapidity, and as this limit is 

 approached there will be a division of the energy of the electric 

 impidse between the electrified molecules and the ether-vortices, 

 and in the end all the energy of the discharge will be confined 

 to the latter. 



The reason for the non-appearance of the rays under ordinary 

 conditions is not that the rays cannot reach the walls of the 

 enclosure or pass through them, but that they cannot form at all. 

 The propagation of vortices in straight lines, the absence of 

 interference phenomena, of reflection, refraction and polarisa- 

 tion, follow from the properties of vortices, and from the absence 

 of anything corresponding to a wave-front. The passage of an 

 ether-vortex through a mass of matter may be compared with a 

 passage of a smoke-ring through a wire gauze screen or a series 

 of such : and as the motion of the rings is more impeded the 

 greater the diameter and the number of wires per unit volume, 

 so, the greater the number and the size of the molecules — that 

 is, the greater the density — the more effective will the medium 

 be in dissipating the energy of the ether-vortices. 



The production of fluorescence, actinic effects, and the dis.si- 

 pation of electric charges by light (which is an ether motion) 

 would make it at least probable that similar (though perhaps 

 not identical) eft'ects would be produced by the motions of 

 ether vortices. 



Prof. J. J. Thomson has measured the velocity of kathode 

 rays and obtained a result so very far less than the velocity of 

 light as to preclude entirely the idea of there being any con- 

 nection between the two. If these results can be made to apply 

 to the .\-rays, the analogy with the properties of smoke-rings 

 would lead us to expect such a result. The Icathode rays have 

 been shown by Lenard to have a considerable range in their 

 properties, depending on the mode of their origin.- It seems 

 likely that their velocities are to a considerable extent dependent 

 on the potential and the suddenness of the electrical impulse ; and 

 if this were .shown to be true of the X-rays, it would be to that 

 extent a confirmation of the theor)'. 



1 A possible objection occur* to the formation "f elher-vortices in a 

 medium which is usually considered free from visco-ity ; but the fact that 

 vibrating molecules can and do communicate their motions to the surround- 

 ing ether shows that the communication of vortex motion may also be 

 possible. 



Thoush not a necessary part of the theory, it may be considered that 

 the expulsion of the ethcr-vorticcs is due to an accumulation of ether in 

 the kathode, and this would lend support to the theory that this accumula- 

 tion is not merely a result of the negative charge, but that this excess of 

 ether is what constitutes the negative charge. 



- The distinction between the X-rays and the kathwde rays appears to be 

 somewhat arlilicial. .-ind it seems probable that the X-rays are only kathode 

 rays sifted by the various media they h: 



NO. 1 386, VOL. 54] 



The foregoing evidence may be considered scarcely sufficient 

 to entitle the proposition here advocated to the dignity of a 

 theory, but it may at least merit consideration as a working 

 hypothesis which may serve as a guide in future experiment. 

 Albert A. Michelson. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Oxford. — The Oxford University Junior Scientific Club will 

 hold a conversazione on Tuesday evening. May 26. The rooms 

 and laboratories of the University Museum, Oxford, will be 

 thrown open by permission of the delegates and professors, and 

 apparatus and experiments illustrating recent progress in the 

 various branches of natural science will be exhibited. During 

 the evening Prof. Silvanus P. Thomson will give a lecture on 

 "Luminescence," with demonstrations. 



On Tuesday, June 2, before the above Club, Prof. W. Ramsay, 

 F. R.S., will deliver the fifth annual Robert Boyle Lecture, on 

 " Argon and Helium, the two recently discovered gases." The 

 "Robert Boyle Lecture" was instituted in 1S92, and the 

 lecturers hitherto have been Sir Henry Acland (1S92), Lord 

 Kelvin (1S93), Prof. A. Macalister (1894), Prof. A. Crum Brown 

 (1S95). 



The vacancies in the Public Examinerships in the Honour 

 School of Natural Science have been recently filled up as 

 follows : — In Animal Morphology, Prof. E. Ray Lankester and 

 Mr. Adam Sedgwick ; in Botany, Prof. D. H. Scott and Mr. 

 R. W. Phillips ; in Geology, Prof. A. H. Green and Mr. J. E. 

 Marr ; in Physics, Mr. R. E. Baynes ; in Chemistry, Prof. W. 

 Ramsay ; and in Animal Physiology, Prof. C. S. Sherrington. 



The -Scholarships and Exhibitions advertised for proficiency in 

 Natural Science are not numerous this year. Merton and New 

 College oft'er each one, the examination to be held conjointly by 

 the two colleges at the end of June. Magdalen offers one or 

 more Demyships in Natural Science for competition in October, 

 and the Delegacy of Non-Collegiate Students offers a scholarship 

 for Chemistry. There seems to be a tendency at the present time 

 to curtail the number of scholarships in Natural Science. 



The Hope Professor of Zoology is giving a course of public 

 lectures at the Museum, on the Hope Collections. The second 

 lecture of the series will be given on Wednesday, May 27, at 

 2. 30 p. m. 



Prof. H. A. Miers, F.R.S., Waynflete Professor of Miner- 

 alogy, gave his inaugural lecture at the University Museum on 

 Wednesday last. 



A Decree will be proposed on the 26th inst. providing for the 

 enlargement and alteration of certain rooms in the University 

 Museum, in order that they may be adapted to the purposes of 

 the Professor of Mineralogy. 



Mr. G. F. Scott EUiot gave a lecture to the Ashmolean 

 Society last Monday, on the race elements of South Africa. 



Cambridge. — The dates of the examinations for entrance 

 scholarships and exhibitions in Natural Science at the several 

 colleges during the next academical year, have been announced 

 as follows : — St. John's and Trinity, November 3, 1896 ; Pem- 

 broke, Caius, King's, Jesus, Christ's, and Emmanuel, November 

 17, 1896; Peterhouse and Sidney, Clare and Trinity Hall, 

 December 8, 1S96 ; Downing, April 20, 1897. The subjects 

 are in General Chemistry, Physics, Zoology, Botany, Geology, 

 and Physiology, two or more sciences being required. Ap- 

 plication for particulars should be made to the respective tutors 

 some weeks before the date of the examination. The yearly value 

 of the scholarships varies from ^So to £\o. 



Vacancies for students of Biology at the University tables in 

 the Zoological Stations of Naples and Plymouth are announced. 

 Applications to occupy the.se are to be sent to Prof. Newton 

 by May 27. 



The University of Utrecht will celebrate the 260th anni- 

 versary of its foundation on June 22 and five following days. 



Mr. John H. Rockefeller has given to Vassar College 

 (women s) 100,000 dols. for a new building, to be either dormitory 

 or recitation hall. 



Mr. Andrew C.\rnec.ie has given to the city of Duquesne, 

 Iowa, a library, gymnasium, and public bath. The buildings 

 are to cost 150,000 dols. 



