484 



NATURE 



[December 31, 1914 



numerable manifestations of adsorption. The 

 recognition of all these factors will naturally be 

 a somewhat arduous task, but will furnish at the 

 very least a new method of attacking problems 

 which cannot be solved by chemistry — in its 

 narrower sense — alone. E. Hatschek. 



FROF. J. W. HITTORF. 



THE death of Johann Wilhelm Hittorf, at the 

 age of ninety years, removes an eminent 

 and honoured leader from the ranks of German 

 physicists. Born and brought up in Bonn, 

 Hittorf devoted himself to the study of mathe- 

 matics and natural science at the Universities of 

 Bonn and Berlin, and became Doctor of Philo- 

 sophy in 1846. Shortly afterwards he attached 

 himself, as privatdocent, to the Academy (later 

 the University) of Miinster in Westphalia, the 

 institution with which he was to be associated 

 during his lifetime. Appointed " ausserordent- 

 licher " professor in 1852, Hittorf became full 

 professor of physics and chemistry four years 

 later, and this post he held till 1879. On the re- 

 organisation of the institution in that year, the 

 chair of physics and chemistry was divided, and 

 Hittorf continued as director of the physical 

 laboratories until serious illness compelled him, 

 in 1889, to seek relief from active teaching work. 

 With rest came recovery and renewed activity, 

 to such good purpose that between his seventieth 

 and eightieth years Hittorf published some half- 

 dozen memoirs. He died on November 28 last, 

 as professor emeritus of the University of 

 Miinster, full of years and honour. 



Hittorf's investigations dealt with a number 

 of problems on the borderland of physics and 

 chemistry, and the results are embodied in about 

 thirty communications to scientific journals. In 

 appraising this output of original work, it must 

 be borne in mind that the earlier researches were 

 carried on under serious disadvantages in respect 

 of laboratory equipment, and that he himself was 

 personally responsible for all the experimental 

 work described in these memoirs. 



Some of the first researches were concerned 

 with the allotropy of selenium and phosphorus, 

 and the discovery of the so-called " metallic " 

 variety of the latter element was made by Hittorf. 

 This work, however, is quite overshadowed by 

 the remarkable series of investigations (published 

 1853-9) on the migration of the ions during 

 electrolysis. Whilst Faraday had studied mainly 

 the nature and the quantity of the substances pro- 

 duced at the electrodes by electrolytic decom- 

 position, Hittorf investigated the more subtle 

 changes of concentration that take place in the 

 electrolyte itself. From these concentration 

 changes, the relative rates at which the ions of 

 an electrolyte move during the passage of a 

 current, and their relative share in the transport 

 of the electricity, were deduced. 



This work met with practically no recognition 

 from Hittorf's contemporaries, and indeed was 

 vigorously attacked by the leading German 



NO. 2357, VOL. 94] 



physicists of the time. Twenty years later the 

 significance of these investigations began to be 

 appreciated, and fortunately Hittorf lived to see 

 his great work accepted as a fundamental part 

 of the science of electrochemistry. 



A prominent place among Hittorf's researches 

 must be assigned also to investigations, carried 

 out at the suggestion of his master Pliicker, on 

 the spectra of ignited gases and vapours. The 

 memoir embodying this work, which was published 

 in the Philosophical Transactions for 1865, deals 

 with the plurality of spectra, and shows, more 

 especially for the case of nitrogen, that the same 

 substance can give two different spectra. Hittorf's 

 association with Pliicker may be further traced 

 in a series of important papers on the passage of 

 electricity through gases ; the foundation of what 

 is known regarding kathode rays, discovered by 

 Pliicker in 1859, was laid in these investigations. 



The remarkable activity of Hittorf's later years, 

 already referred to, was shown chiefly in a study 

 of the passivity of metals, more especially 

 chromium ; it was found that this phenomenon 

 cannot be attributed to the presence of a film of 

 oxide on the surface of the metal. It is a striking 

 fact that in his last published memoirs Hittorf 

 returns to the transport of electricity in electro- 

 lytes, the field of research in which he laboured 

 fifty years before, and with which his name will 

 be inseparably associated. 



J. C. P. 



DR. N. C. DUNER. 

 HTHE death of Nils Christoffer Duner has 

 J- deprived Sweden of one of her most distin- 

 guished men of science, and astronomy of an 

 active and devoted student. Born on May 21, 

 1839, Duner entered the University of Lund in 

 1855, and took his doctor's degree in 1862, He 

 became a member of the staff of the Lund Observa- 

 tory in 1864, and occupied that position until his 

 appointment, in 1888, as Professor in the Univer- 

 sity and Director of the Observatory of Upsala. 

 He died at Stockholm on November 10, after a 

 brief illness following his return from a journey 

 to observe the solar eclipse of last August. 



Duner made notable contributions to many 

 departments of astronomy, and his name will be 

 especially remembered in connection with his work 

 on double stars, variable stars, the spectra of red 

 stars, and the investigation of the sun's rotation 

 by the spectroscopic method. His work on 

 double stars during the years 1867 to 1875 at 

 once placed him in the front rank of double-star 

 observers and computers. 



Several variable stars were discovered or in- 

 vestigated by Duner. Two of them— Y Cygni 

 and Z Herculis — have proved to be of exceptional 

 interest. Duner not only found that the light- 

 changes of these stars could be completely ex- 

 plained by supposing them to be eclipsing variables 

 of the Algol type, with the difference that both 

 components are bright, but was able to determine 

 the elements and dimensions of the two systems. 



