November 30, 1893] 



NA TURE 



117 



late, but so much has been written at second-hand, as well as in 

 the way of ori;;inal treatment, that further reiteration is uncalled 

 for. The work of Hertz and of his host of followers is familiar 

 to us all. In the study of electrical oscillations even of very 

 high frequency, photography has been used with success, and 

 details of the phenomena of time-elements truly infinitesimal 

 have been secured. By the labours of Wiener ^ waves of a 

 still higher order than those which have occupied the attention 

 of the electrician have been photographed, and a new field of 

 the greatest promise'has been thrown open to the optician. The 

 isolation of a single light vibration may indeed still be as far 

 from us as is the inspection of the molecule by means of the 

 microscope, but in the meantime we have in the photography 

 of a system of standing light-waves, an achievement well worth 

 celebrating. 



In the investigation of the phenomena of the time-infini- 

 tesimal, so far as periodic changes are concerned, we see that 

 the experimenters of the present time are gaining much of 

 detailed knowledge. There is another field equally important, 

 in my opinion, which is as yet for the most part unexplored. 

 The study of the beginnings of changes brought about by abrupt 

 shifting of the conditions of equilibrium is one from which very 

 much may be expected. Already suggestive beginnings have 

 been made, but the researches have not been pushed to the 

 limit of theexperimentally possible. Oftentimes interesting obser- 

 vations of what might be termed "startling phenomena" have 

 been recorded, but quantitative results are lacking. Take for 

 example the brilliant work of Becquerel [Comptes rendus, 96, 

 pp. 121, 1215, 1853) with the phosphorescope. What a mass 

 of fascinating and suggestive material that savant has gathered 

 into the first volume of his book on light ! {La Liinuire, i. pp. 

 206-422.) What a world of interesting material these pre- 

 liminary observations present to him who shall undertake to 

 determine quantitatively, wave- length by wave-length, the 

 changes which the radiations from the numerous luminescent 

 materials undergo, beginning with the instant of exposure and 

 following the vanishing light until it is gone. 



Of a few isolated cases which have been forced upon us by 

 their practical importance we have some complete knowledge 

 already. With the phenomena, in cables when current is 

 suddenly introduced or circuit is broken, we are reasonably 

 familiar. The case of the charge and discharge of condensers 

 has been treated analytically under assumptions the precise 

 truth of which is still to be verified. The detailed study by ex- 

 periments carried to the utmost refinement, of the very cases 

 which seem to have been most completely covered by theory, 

 is especially important ; since in this way only can the assump- 

 tions upon which our analysis is based be rigorously determined, 

 and the necessity of modifications be ascertained. For some 

 of this work methods already in use in the study of periodic 

 phenomena will suffice. The curve-writing voltmeter, for ex- 

 ample, may be made to give records running to within a 

 thousandth of a second of the instant when a process such as 

 electrolysis, electrolytic polarisation, voltaic action, or the 

 charge and discharge of a condenser begins. Instruments such 

 as the von Helmholtz pendulum, for the isolation of definite 

 small time intervals, may also be applied to a great variety of 

 progressive phenomena, enabling us to approach by successive 

 steps almost to the very beginnings of the changes to be ana- 

 lysed. Concerning known methods let me point out, in con- 

 clusion, that photography with the moving plate is a means, the 

 limitations of which have not yet been discovered. It is equally 

 applicable to periodic and to progressive phenomena, often 

 with results of unexpected beauty and significance." 



The remarkable experiments of Mach ( Wiener Sitziingsberichte^ 

 95, p. 764, also 97, p. 41) and of Boys ("On Electric Spark 

 Photographs," &c., Nature, vol. xlvii. p. 415) indicate that 

 the dry plate is still abundantly exposed within intervals so short 

 that the swiftest of modern projectiles give images as of a body 

 at rest. 



The laws of electrical resonance have already been so far 

 determined that we can construct condensers, the duration of the 

 discharge of which is a matter of computation, and the precise 



1 "Stehende Lichtwelkn und Schwingungsrichtung des polarisirteu 

 Lichtes." Annalen der Physik N.F. vol. xl. p. 203. 



2 In photographing the alternate current arc a single exposure of a con- 

 tinuous current lamp upon the moving plate, by way of check, brought out 

 the seat and precise nature of the hissing of the arc in a manner scarcely 

 to be reached in any other way. For the method used, see " A Photographic 

 Study of the Electric Arc," Trans. Am. Inst. Electrical Engineers, vol. viii. 

 p. 214, 1891. 



NO. T257, VOL. 40] 



moment of the discharge of which after a given event is quite 

 within control. This single device, consisting of the exposure 

 of the photographic plate by means of a properly timed spark, 

 brings under observation a set of time intervals of a new and 

 higher order of brevity. Much is destined to be learned by 

 means of it concerning the nature of matter, and much more, I 

 think, from other, possibly still more powerful, methods which 

 will doubtless be developed when the importance of the study of 

 the time-infinitesimal is more generally recognised. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE . 



Oxford. — At a meeting of the Ashmolean Society, held 

 at the Museum on Monday, 27th inst., Prof. Odling was elected 

 President for the ensuing year, and Messrs. F. J. Smith and 

 G. C. Bourne were re-elected Secretaries. Mr. E. J. Stone 

 read a paper on the rainfall at Oxford during the last seventy- 

 eight years, and Prof. E. Ray Lankester read a paper on 

 fresh-water jelly-fishes. 



At the meeting of the Junior Scientific Club, on Friday, 

 24th inst., papers were read by Dr. Ritchie, on anthrax spores 

 and bacilli ; by Mr. G. B. ,Cronshaw, on explosions in coal- 

 mines ; and by Mr. A. L. Still, on plants and their standing 

 army. 



Cambridge. — The Special Board for Physics and Chemistry 

 report that the Cavendish Laboratory, founded and equipped 

 by the munificence of the late Duke of Devonshire, has become 

 incapable of accommodating the large number of students de- 

 siring tuition in Physics. In the present term no less than 135 

 students are at work in a disused galvanised iron dissecting- 

 room, which, on its vacation by the Professor of Anatomy, has 

 been placed at the disposal of the Professor of Physics as a tem- 

 porary laboratory. Its site will, however, soon be required for 

 the Sedgwick Memorial Museum of Geology, and the Board feel 

 that the time has come for the permanent extension of the 

 Cavendish Laboratory. An adjoining site is available between 

 it and the Engineering Laboratory ; but the problem of funds 

 for building and equipment is less easy to solve, unless a bene- 

 factor as generous as the late Chancellor should make his appear- 

 ance. The high position deservedly held by the Cavendish 

 Laboratory, entrusted as it is with much work of national 

 importance, makes it reasonable to hope that Prof. J. J. 

 Thomson will be able to obtain the means for the desired 

 extension. 



Mr. W. Gardiner and Mr. A. C. Seward have been re- 

 appointed University Lecturers in Botany, and Dr. Hill, Master 

 of Downing College, Lecturer in Advanced Human Anatomy, 

 for five years. Dr. Hill has also been appointed Chairman of 

 the Examiners for the Natural Sciences Tripos. 



The Local Examinations Syndicate report that the work done 

 in the scientific branches of the Higher Local Examinations 

 during the past year was on the whole satisfactory. Imperfect 

 experimental work in chemistry, and lack of practical instruction 

 in zoology, are among the weaker points revealed. 



The Examinations in Sanitary Science seem to be increasingly 

 appreciated by medical men. During the present year eighty- 

 seven candidates have presented themselves, and of these fifty- 

 eight received diplomas in Public Health. 



The Times correspondent at Paris says that an International 

 University alliance is in course of formation there. Its object 

 is to facilitate the passing of students from one University to 

 another, to promote travelling scholarships and the exchange of 

 information, to multiply periodical celebrations, and to "draw 

 the attention of the Universities to the question of introducing 

 greater justice into international relations." 



SCIENTIFIC SERIALS. 



Wiedtnami s Annalen der Physik tend Chetnie, No II. — On 

 the speed of electrolytic ions, by F. Kohlrausch. This is a 

 compilation of tables of absolute velocities, of mobilities, and 

 of coefficients of electrolytic friction according to the latest and 

 most reliable data. — Contributions to the knowledge of the 

 absorption and branching of electric oscillations in wires, by 

 Ignaz Klemencic. — The resistance which causes evolution 

 of heat during the passage of very rapid oscillations depends 

 upon the magnetic permeability of the wire, but in a different 



