February 



1910J 



NA TURE 



403 



afterwards shown to be appreciably in error, was of 

 considerable importance historically, since it directed 

 attention to the necessity of examining further the 

 result obtained in 1S63 and 1S64 by Maxwell and his 

 coadjutors for the British Association Committee on 

 Electrical Standards. 



In 1871 Kohlrausch introduced a method for mea- 

 suring the electrical resistance of electrolytes founded 

 upon the employment of alternating currents gener- 

 ated by the revolution of a magnet inside a coil of 

 wire, the relative positions of magnet and coil being 

 like those in an ordinary galvanometer. In this way 

 the disturbing effect due to the polarisation of the 

 electrodes was in a great measure, if not entirely, got 

 rid of, and the results obtained were a great advance 

 in respect of accuracy upon those previously obtained. 

 In later modifications of the method the alternate 

 currents of an induction-coil were used. This investi- 

 gation formed the starting point of a long series of 

 researches into the conducting power of electrolytic 

 solutions. The examination of a great number of 

 soluble salts in aqueous solutions of different concen- 

 trations showed . that, although the conductivity 

 decreases with decreasing concentration, the ratio of 

 conductivity to concentration increases, at first nearly 

 uniformly, but approaches a definite limit for each 

 salt when very small concentrations are reached, that 

 is, when the solutions are very dilute. It was further 

 found that, when the proportion of salt in solution was 

 expressed in terms of the equivalent mass of the salt, 

 tlie limiting (maximum) value of the above ratio 

 varied within comparatively narrow limits for a great 

 number of salts. .Another important result of 

 Kohlrausch's experiments was the establishment of 

 a simple relation between the conductivities of dilute 

 solutions and the mobilities, as deduced from Hittorf's 

 measurements, of the ions into which the respective 

 salts may be supposed to be broken up when dissolved. 



Kohlrausch rendered an extremely valuable service 

 to the teaching of experimental physics by the publi- 

 cation, in 1870, of his " Leitfaden der praktischen 

 Physik." This was the first, and, in the writer's 

 opinion, the best of numerous works of the same kind 

 that have since appeared in various countries, designed 

 to guide students of physics in a systematic course of 

 practical work in the physical laboratory. The high 

 appreciation it has met with is shown by the number 

 of editions that have been called for — it reached the 

 eighth in i8q6 ; it was translated into English by 

 Messrs. T. H. Waller and H. R. Procter soon after 

 its first appearance, and a second English edition was 

 published in 1883. G. C. F. 



SIR CHARLES TODD, K.C.M.G.. F.R.S. 

 ■pEW men have lived a fuller life or given more 

 -•- freely of their best than Sir Charles Todd, whose 

 death we deeply regret to record. It is only about 

 three years ago that he retired from active service, 

 but he was then above eighty years of age and his 

 career had been unusually long. His scientific life 

 dates back to 1841, when he entered the Royal Obser- 

 vatory, Greenwich. The instruments, as those who 

 used them, have passed away, and he must have been 

 the last survivor of the little band who worked with 

 the old meridian transit and circle. There he acquired 

 a training in scientific methods which he was des- 

 tined to turn to such useful account in promoting the 

 interests of a new colony. In South Australia he 

 found his work, and there his memory will be trea- 

 sured. For it was his fortune to organise two 

 departments, the Post Office and the Meteorological 

 Service, which have contributed in no small degree to 

 the growth of that thriving settlement. 



It is not given to many to see their exertions and 

 NO. 2101, VOL. 82] 



plans so speedily and completely successful as did 

 Sir Charles Todd, or to fill simultaneously the three 

 important positions of Postmaster-General, Superin- 

 tendent of Telegraphs, and Government Astronomer. 

 But it will be admitted that he filled this trinity of 

 offices with credit to himself and to the advantage of 

 others. The Post Office was practically his own 

 organisation, which, continually growing with the 

 requirements of the Colony, proved itself equal to the 

 increasing demands. It was in connection with the 

 establishment of the Telegraph Service, and its grow- 

 ing needs, that he made that remarkable ride of 2000 

 miles across the arid interior of the continent of 

 -Australia, from Adelaide to Port Darwen. The energy 

 and intrepidity of the man were well illustrated by 

 this memorable venture. No wonder that he loved to 

 tell of that day, when he sat on the ground near 

 Mount Stewart, amid uncomfortable surroundings, 

 but forgot all in the sense of successful achievement, 

 when, with a little pocket relay, he connected the wires 

 and held communication with the extreme north and 

 south of the island. 



As Government Astronomer, it will be remembered 

 that Sir Charles Todd took part in organising the ex- 

 peditions for the observation of the transit of Venus, 

 that he kept the 8-inch refractor steadily at work, and 

 did what lay in his power to maintain an interest in 

 astronomy. Still greater was the service he rendered 

 in promoting a meteorological and climatological ser- 

 vey — so necessary in a new countr}', where the 

 climatic conditions are of vital importance to the 

 incoming settler. For something like forty years he 

 maintained the meteorological service, and has left 

 to his successor a complete and well-equipped organi- 

 sation. 



His talents were admirably fitted for the field in 

 which they found scope. He knew how to inspire 

 others with the tireless energy that carried him 

 through so many difficulties; his geniality secured 

 him many friends and willing workers that enabled 

 him to accomplish so much; his life and history are 

 written in the progress of the colony during the last 

 fifty years. Amid the regrets of those among whom 

 he laboured so well and so long, he will be remembered 

 as one whose services gained the approval of his 

 sovereign and the cordial appreciation of his scientific 

 colleagues, and especially as a typical specimen of that 

 class which, great in resolve as in achievement, has 

 given strength and impulse to our Colonial Empire. 



NOTES. 



At the meeting of the Paris Academy of Sciences on 

 January 24 Lord Rayleigh was elected a foreign associate 

 member in succession to the late Prof. Simon Newcomb. 

 Lord Rayleigh was elected a correspondant of the academy 

 in 1S90. 



M. Emmanuel de Margerie has been elected president 

 for 1910 of the Paris Geographical Society, and M. H. 

 Deslandres and Colonel Bourgeois vice-presidents. 



During his recent visit to St. Petersburg, Sir Ernest 

 Shackleton was presented with the Constantine gold medal 

 of the Russian Geographical Society. 



The Lettsomian lectures on " The Cerebellum and its 

 Affections " will be delivered by Dr. J. S. Risien Russell 

 at the Medical Society of London on February 7 and 21 and 

 March 7. 



At the close of a public lecture by Dr. Sven Hedin in 

 Rome on January 30, the King of Italy handed to him 

 the large gold medal which has been conferred upon him 

 by the Italian Geographical Society. 



