December 30, 1909] 



NA TURE 



Prut. Roberts-Austen, then one of the secretaries; he 

 kindly gave me an introduction to Prof. Adams, the 

 president, and the two were good enough to sign my 

 recommendation form. Who furnished the third 

 signature I never ascertained. In spite of this some- 

 what inauspicious debut, it was my good fortune after, 

 and solely as the result of, a few years' more or less 

 regular attendance at the meetings to have made a 

 large number of acquaintances, and, I may say, very 

 good friends, among the leaders and workers in 

 science. I have long regarded my connection with 

 the Physical Society as the source of one of the chief 

 interests of my life; and for the highly valued honour 

 you have done me in electing me to be your president, 

 I cannot sufficiently express my thanks." 



Bidwell's first cominunication to the Physical Society 

 was read on March 13, i88o; it was entitled "On 

 the Influence of Friction upon the Generation of a 

 Voltaic Current," and was a simple investigation into 

 the causes of the operation of the Edison "motograph " 

 or chalk-cylinder telephone receiver. He considered 

 his e.xperiments to show conclusively that the explana- 

 tion of the changes of friction in that instrument is 

 the electrolytic Ifljeration of a film of hydrogen gas. 

 For the next three or four years he was chiefly 

 occupied which the photo-electric properties of 

 selenium. He invented a method of telegraphic 

 photography based on the use of selenium. In the 

 course of his work he did much to clear up the 

 obscurities and contradictions which until then had 

 hung over the behaviour of selenium. Being himself 

 an excellent mechanic, and having equipped for him- 

 self a workshop in his house, he constructed, with his 

 own hands, many simple and beautiful experimental 

 appliances. His method of constructing selenium cells 

 with copper wires wound upon a slip of slate or of 

 mica brought selenium cells within the reach of all 

 experimenters. He investigated the effects of tem- 

 perature and of moisture upon selenium cells. He 

 also investigated the kindred properties of cells made 

 with mixtures of sulphur and carbon. The next 

 subject to claim his attention was the alleged change 

 ill the resistance of carbon under pressure, which led 

 him to a careful investigation of the whole question 

 of microphonic contacts. In an article communicated 

 to the Royal Society, he considered the methods of 

 measuring the electrical resistance of contacts, and 

 found tliat though the moment before the measure- 

 ment is made the resistance may be sensibly infinite, 

 the very act of measurement reduces it to a few 

 hundred ohms. Here he touched the question of the 

 coherer, which was destined in a short space to become, 

 in the hands of Branly and of Sir Oliver Lodge, so 

 vastly important for the study of radio-telegraphy. 



Bidwell was always a most conscientious worker, 

 never satisfied to publish until he had convinced him- 

 self of the reality of his results, and of their 

 originality. He took endless pains to discover what 

 might liave been previously published on any subject 

 at which he was working. He had a curious distrust 

 of himself while at work, coupled with a singular 

 confidence in the results when they were once estab- 

 lished. He had a profound dissatisfaction with half- 

 knowledge, but yet those subjects as to which 

 knowlf-dge was in an imperfect stage possessed for 

 him n singular fascination. Most of his work con- 

 sisted in unravelling paradoxical facts or obscure 

 phenomena. Thus he investigated the magnetic 

 expansion of iron, and cleared away the obscuritv 

 involved in the case of straight rods by the action of 

 their poles, by showing that an iron ring (which 

 possesses no poles) also expands on being magnetised. 

 In connection with this subject, he re-examined the 

 law of magnetic traction. He was the discoverer, too, 

 of the paradoxical fact that an iron electromagnet, if 

 NO. 2096, VOL. 82] 



its core is made of an iron tube with short plugs fitting 

 loosely into its ends, when it is magnetised grows 

 longer by pushing the plugs out, instead of attracting 

 them in. Later, and by a beautifully refined piece of 

 home-made apparatus, he showed that the impact of 

 light is able to affect directly the magnetic state of a 

 carefully demagnetised soft iron rod. 



His attention was then directed to the subjective 

 phenomena of vision, and he made innumerable ex- 

 peiiments on the "ghosts" that are seen following in 

 the train of a luminous body moving across a dark 

 field. He produced some very extraordinary and 

 paradoxical illustrations of colour-vision by inter- 

 mittent illumination and vision of coloured objects, 

 which he caused to appear of tints complementary to 

 their actual pigments. The result of these investiga- 

 tions he embodied in a most interesting book, written 

 in a popular style, but essentially scientific throughout, 

 called "Curiosities of Light and Sight," published in 

 1899. He lectured more than once on these matters 

 at the Royal Institution. Unhappily, in his experi- 

 ments his e)'esight became seriously impaired, and 

 he was threatened with blindness. Fortunately, how- 

 ever, after many months he recovered, and was able 

 to read without pain. In 1900, Bidwell received from 

 his own University of Cambridge the degree of 

 D.Sc. He had been elected a Fellow of the 

 Royal Society in May, 18S6 ; and he served on 

 the council of that society from 1904 to 1906. His 

 presidency of the Physical Society in 1897-9 has 

 already been alluded to. Amongst his later work was 

 the writing of the article on magnetism for the 

 new volumes of the " EncyclopEedia Britannica." In 

 consequence of troubles arising from an affection of 

 the heart, Shelford Bidwell had not been able to attend 

 any scientific meetings for more than eighteen months, 

 his last visit to the Royal Society being in May, 1908. 

 He died on December iS at his residence, 

 " Beechmead," Oaklands Chase, Weybridge, at the 

 age of sixt3'-one. 



DR. R. BOWDLER SHARPE. 



T T is with great regret that we have to record the 

 ■•• death of Dr. Richard Bovvdler Sharpe, at his 

 residence in Chiswick, on December 25. Although 

 Dr. Sharpe had been in indifferent health for some 

 considerable time, he was on duty at the Natural 

 History Museum at least as late as December 14, so 

 that the fatal attack was of comparatively short 

 duration. 



Born in November, 1S47, and therefore just over 

 sixty-two years of age at the time of his death. Dr. 

 Sharpe was the son of T. B. Sharpe, a publisher, of 

 Cookham and Malvern Link. Educated at Brighton 

 and at Peterborough and Loughborough grammar 

 schools, he entered the service of Messrs. W. H. Smith 

 and Son at the early age of sixteen, and after re- 

 maining two years with that firm, migrated in 1865 

 to the establishment of Mr, Quaritch. Two years 

 later he was appointed to the newly-founded librarian- 

 ship of the Zoological Society of London, a position 

 which brought him into contact with Dr. P. L. Sclater, 

 and thus no doubt tended to foster that taste for 

 ornithology with which he had been imbued from very 

 early years. Be this as it may, by 1872 Dr. Sharpe 

 had become an accomplished ornithologist, and he was 

 appointed in that year to a senior assistantship in the 

 zoological department of the British Museum, a 

 position from which he was promoted to an assistant- 

 keepership in the vertebrate section in 1895, this latter 

 post being held by him at the time of his death. 



Dr. Sharpe was a Fellow of the Linnean and 

 Zoological Societies, an LL.D. of Aberdeen LTniversitv, 



