September i, 1898] 



NATURE 



419 



and not a little vigilance is necessary to protect it 

 from dishonest visitors, attempting to purloin teeth or 

 fragments. It has been beautifully photographed by Mr. 

 H. Elkington, of Broadwell, Rugby (a reproduction of the 



photograph accompanies this notice), who will, on applica- 

 tion, furnish copies to geologists and others desiring 

 them. W. T. 



DR. JOHN HOP KINS ON, F.R.S. 

 'X'HE news that Dr. John Hopkinson, F.R.S. , met his 

 -■• death in a terrible mountain accident on Saturday 

 last, has been received with deep regret in the scientific 

 world. His name is familiar to every student of elec- 

 tricity and its applications, and by his death electrical 

 science has lost one of its most active and brilliant 

 workers. It appears from the telegraphic reports that 

 Dr. Hopkinson, who was a practised mountaineer, 

 started from Arolla on Saturday morning, with his son 

 John and two daughters, to ascend the Petite Dent de 

 Veisivi, one of the striking points dominating Evolena, 

 in the Val d'Hdrens, running south from the Rhone 

 Valley at Sion. The ascent is not considered a very 

 dangerous one, and the party went without guides. 

 Nothing haying been seen of them on Saturday night, 

 search parties were organised, and the melancholy dis- 

 covery was made that a catastrophe had occurred, the 

 dead bodies of Dr. Hopkinson and his three children 

 being found roped together, but terribly mutilated, at the 

 foot of the highest cliffs. How the accident happened is 

 not known, but probably one of the party slipped whilst 

 climbing a cliff, and ail four then fell from rock to rock 

 several hundred feet to the moraine below. Like Francis 

 Balfour and Milnes Marshall, Dr. Hopkinson has lost his 

 NO. 1505, VOL. 58] 



life while mountain climbing, and like them also he leaves 

 behind a rich record of work done for the advancement 

 of science. 



Dr. Hopkinson was born at Manchester in 1849, and 

 was the eldest son of Alderman Hopkinson, an ex-Mayor 

 of that city. In his sixteenth year he went to Owens 

 College, where he remained for two years and a half, and 

 then went to Trinity College, Cambridge. In 1871 he 

 was Senior Wrangler and First Smith's Prizeman, and 

 was appointed fellow and tutor of his college. While at 

 Cambridge he obtained the D.Sc. degree at London 

 University. Referring some years later to the influences 

 which helped to mould his career, he said : — 



" My father cultivated in me a taste for science from a 

 time before I can remember ; my mother gave me the 

 first systematic instruction of which I have any recollec- 

 tions. If my father gave me my first taste for science,, 

 you may be sure that taste was encouraged at Owens 

 College. Mathematics is the most essential weapon of 

 the physicist, and nowhere can mathematics be learned 

 as at Cambridge. I owe to Sir William Thompson the 

 first impulse to experimental work in electricity and 

 magnetism. He has been to me for many years the 

 kindest of friends, always ready to encourage and \.o 

 help." 



After leaving Cambridge Dr. Hopkinson was for six 

 years with Messrs. Chance and Co., near Birmingham,, 

 as their engineer. He removed to London in 1878, and,, 

 after commencing practice as a general engineer, took 

 up electrical engineering, in which branch of applied 

 science his most valuable investigations have been 

 accomplished. He was elected a Fellow of the Royal 

 Society in 1878, and received one of the Royal Medals 

 of the Society in 1890, for his researches in magnetism 

 and electricity. In presenting the medal, the President 

 pointed out that Dr. Hopkinson's researches comprised 

 investigations of the effect of temperature upon the 

 magnetic properties of iron, nickel, and various alloys of 

 these metals. Before these investigations were published 

 it was thought that increased temperature tended to 

 diminish the magnetic susceptibility of iron. Dr. 

 Hopkinson's experiments showed, however, that, on the 

 contrary, the magnetic susceptibility increases enor- 

 mously as the temperature increases, until the temper- 

 ature reaches about 660^ C. ; beyond this temperature 

 iron entirely ceases to be magnetic. He also made a 

 series of determinations of the specific inductive capaci- 

 ties and refractive indices of a large number of trans- 

 parent dielectrics, the results of which are of great 

 importance in the theories of electricity and light. Irk 

 addition to these researches, he introduced many im- 

 provements into lighthouse equipment, notably the 

 "group flashing apparatus." 



Dr. Hopkinson's contributions to the theory of dynamo- 

 electric machinery are most important ; and to him elec- 

 tricians owe the method, now so extensively used, of 

 solving problems relating to dynamos by the use of the 

 "characteristic curve." On the subject of dynamc>- 

 electric machinery Dr. Hopkinson was, indeed, a leading 

 authority. A volume containing a number of his papers 

 on this and allied subjects was published in 1892, and it 

 constitutes a valuable testimony to the scientific and prac- 

 tical importance of his researches. The work contains an 

 account of a very complete and exhaustive set of experi- 

 ments on dynamo machines under working conditions^ 

 and graphical representations of the results. In referring 

 to Dr. Hopkinson's work in these columns, the reviewer 

 remarked : "No device in the whole history of the 

 evolution of the dynamo has been of more general service 

 than his plan of exhibiting the results of experiments in 

 the well named characteristic curve of the machine. This 

 did for the dynamo what the indicator diagram had long 

 been doing for the steam engine, though not, of course, 

 in the same way. With the most admirable simplicity 



