474 



NATURE 



[March 15, 1900 



For forty-eight years Dr. Carl Theodor Robert Luther 

 worked unremittingly with the small instruments of the 

 Diisseldorf Observatory, and few men have won so 

 much satisfaction and rendered such essential services 

 with apparently inadequate means. When, a half cen- 

 tury ago, he began to direct the fortunes of the little 

 Observatory of Bilk, the discovery and the observation of 

 small planets still awakened considerable interest in the 

 astronomical world, and he perceived that a small 

 observatory, somewhat meanly equipped, could not 

 undertake a more meritorious service than to devote 

 itself methodically to the study of the movement of 

 these bodies. Resolved to devote himself to this work, 

 he never swerved from it. How well he worked with a 

 six foot equatorial and a simple ring micrometer will 

 readily be admitted by those who have had to use his 

 observations in the discussion of planetary orbits. In 

 this one subject, which he had made his own, his untiring 

 devotion enabled him to compete in accuracy, and in 

 quantity of observations, with other observatories 

 possessing greater optical power and employing more 

 delicate apparatus. He lived to see the branch of 

 astronomical science that he loved and supported become 

 somewhat discredited by the very wealth of material 

 with which the possessors of larger optical means and 

 improved star-charts were able to startle and to over- 

 whelm plodding computers and observers. If observation 

 did outrun computation, Luther, however, made some 

 effort to withstand the onrush, and he succeeded in placing 

 the theory of five of the planets— Hebe, Parthenope, 

 Melete, Danae and Glauke — in such a satisfactory 

 position that they are not likely to be lost. 



But Luther's work began long before he went to Bilk. 

 He was attached to the staff of the Berlin Observatory 

 before Neptune was discovered. He took a share in the 

 construction of the Berlin star-charts, that rendered the 

 actual detection of the planet so simple ; and every one 

 who has used Olbers' method for computing comet orbits 

 will recall with satisfaction Barker's Table of Parabolic 

 Anomalies, "von neuem berechnet von Herrn Stud. 

 Luther." 



Modest honours followed Luther in his simple-minded 

 devotion to astronomy. In 1854, he was elected a 

 Foreign Associate of the Royal Astronomical Society, 

 and in the following year the Bonn University elected 

 him a Doctor of Philosophy. Seven times did the Paris 

 Academy vote him the Lalande Prize for his discoveries, 

 and when the same Academy struck a medal to com- 

 memorate the completion of the first hundred small 

 planets, his portrait appeared on the medal side by side 

 with those of Hind and Goldschmidt, the representatives 

 of Germany, England and France in this special field 

 of research. 



The death of Dr. George Riimker, Emeritus Director 

 of the Hamburg Observatory, is also announced — a 

 name long and honourably connected with the Hamburg 

 Observatory, and associated with much good work. The 

 late director was born at the Observatory, where his 

 father, after his return from Paramatta, was in residence. 

 Early trained to astronomical methods. Dr. George 

 Riimker had the advantage of experience in various ob- 

 servatories, spendmg some time at the Durham Obser- 

 vatory under the late Prof. Chevallier. On his return to 

 Germany he was attached to the Hamburg Observatory, 

 and busied himself with the preparation of a catalogue 

 of circumpolarnebulie. After his appointment as director, 

 the energies of the observatory have been mainly devoted 

 to the observation of planets and comets. These obser- 

 vations, which have been mainly published in the 

 Astronotnische Nachrichten, display a considerable 

 amount of activity ; but in addition to researches of a 

 purely astronomical character. Dr. Riimker had given 

 very considerable attention to all questions connected 

 with the improvement of navigation, and to the testing 



NO. 1585, VOL. 61] 



of instruments required in the service of the marine. 

 The rapid development of the Port of Hamburg has 

 made the testing of chronometers and accurate time dis- 

 tribution matters of prime importance, and the late 

 director fully recognised the desirability of ministering to 

 the necessities of the port. 



DR. THOMAS PRESTON, F.R.S. 



WITH sincere regret we announce the death of Prof- 

 Thomas Preston, which occurred at his residence 

 in Dublin on March 7. Still a young man, the event, 

 although preceded by a tedious illness, came as a shock 

 to his friends, and we believe will be learned with sorrow 

 by every scientific man in this country. Abroad, too, his 

 name had recently become well-known in connection 

 with his researches on radiation in the magnetic field. 



Thomas Preston was born in co. Armagh in i860. He 

 graduated both in the Royal University and in Trinity 

 College, Dublin, in each University gaining high dis- 

 tinction in mathematics and experimental science. The 

 first edition of his well-known "Theory of Light" 

 appeared in 1890 ; his "Theory of Heat" in 1895. He 

 filled the post of Science and Art Inspector for Ireland 

 since 1894. He held a Fellowship in the Royal Univer- 

 sity, and also the degree of Doctor of Science of that 

 University ; and was elected a Fellow of the Royal 

 Society in 1898. 



What great promise was in Thomas Preston is known 

 to all who are acquainted with the good scientific work 

 he had already accomplished. The Royal Dublin Society 

 recently conferred upon him the Boyle Medal for dis- 

 tinguished work in the domain of pure science. On that 

 occasion the Science Committee of the Society reported 

 on his work in terms a quotation from which will best 

 serve to convey in a brief notice the scope of Preston's 

 contributions to science. The report more especially 

 relates to his services in connection with radiation in a 

 strong magnetic field, and summarises the part he took 

 in this recent branch of research, as follows : — 



" Early in 1897 the broadening of the spectral lines arising 

 from radiation in a strong magnetic field was announced by Dr. 

 P. Zeeman ; and about the middle of that year, Dr. Zeeman 

 further announced the fact that the triple nature of some of these 

 lines had been established by aid of the differing polarisation of 

 the central and lateral bands. This important experimental 

 work was the first completely successful accomplishment of an 

 experiment undertaken by Faraday, so long ago as 1862. The 

 theoretical aspect of Zeeman's first experiments had been ex- 

 amined by Prof. Lorentz and by Dr. Larmor. The threefold 

 nature of the broadened lines as well as their polarisation phe- 

 nomena had been predicted by these mathematicians, and also 

 the probability that the change of wave-length introduced by the 

 magnetic force should be proportional to the square of the wave- 

 length of the affected lines. 



" Such, briefly, was the state of the inquiry, when Prof. 

 Preston — working with the Rowland Grating of the Royal Uni- 

 versity — brought his first research before this Society towards 

 the close of 1897. (' Radiation Phenomena in a Strong Mag- 

 netic Field,' Trans. R.D.S. vol. vi. Ser. ii. p. 358). 



" Members of this Society who were present on that occasion 

 will recollect that they were treated to no second-hand account 

 of the phenomena, but were shown — a feat not before attempted 

 — the triplication and quadruplication of the lines of cadmium 

 and zinc, by means of photographs projected on the screen. 



" In this communication, Prof. Preston not only showed that 

 he had attained a higher degree of resolution of the lines than 

 had up to this been accomplished, but he was able to announce 

 the existence of quartet and sextet forms for the first time. In 

 his paper he seeks for explanation of the quartet variation from 

 the normal triplet, and the fact that the difference of wave-length 

 introduced by the magnetic farce is not proportional generally to 

 the square of the wave-length (as the simple theory seemed to 

 suggest) was forced upon him at this early stage of his work. 



"Although these matters were laid before the Royal Dublin 

 Society in December 1897, Prof. Preston can lay still earlier 

 claim to these observations, as appears from a short communica- 



