March 13, 1919] 



NATURE 



29 



and, besides utilising- photography in many of his 

 larger undertakings, he showed great ingenuity 

 in devising new applications for special purposes. 

 One of his well-known devices was an instrument 

 for automatically charting the brighter stars on 

 ever}' fine evening; and among numerous other 

 arrangements was one for recording . the rapid 

 changes in brightness of short-period variables 

 by intermittent exposures at short intervals. 



The number of photographs of the heavens now 

 accumulated in the Harvard "library of photo- 

 graphs" must be approaching two hundred 

 thousand. All stars of the nth magnitude, 

 and many fainter ones, are shown over and over 

 again on these plates, and the collection provides 

 the only history that exists of the stellar universe. 

 When any new object is discovered, as in the case 

 of the planet Eros, or the recent Nova Aquilae, its 

 past history for many years has almost invariably 

 been revealed by the Harvard plates, and a vast 

 amount of valuable material doubtless still remains 

 to be extracted. 



In forming his plans for the spectroscopic work 

 of the Henry Draper memorial, Pickering again 

 took a large view of his opportunities. The 

 photography of the spectra of stars with a slit 

 spectroscope, one by one, though essential for 

 the precise determination of radial velocities, is 

 of necessity a slow process, and the objective- 

 prism, whereby hundreds of spectra may often 

 be obtained in a single exposure, made a strong 

 appeal to him. The scale of the spectra yielded 

 by this "wliolesale " method is usually small, but 

 it suffices for purposes of general classification, 

 and thousands of stars were soon included in the 

 spectroscopic survey. The first "Draper Cata- 

 logue," forming vol. xxvii. of the Harvard Annals, 

 includes 10,351 stars north of -25°, classified on 

 an alphabetical system, which, with some modi- 

 fications, has become generally adopted by astro- 

 nomers throughout the world. This work has 

 since been continued at Harvard and at Arequipa, 

 and a new Draper catalogue giving the sf)ectra 

 of nearly a quarter of a million stars is now in 

 course of publication. 



Many notable discoveries have been made in 

 connection with the work of the Draper memorial. 

 One of the earliest was that of the p>eriodical 

 duplication of the lines in the spectra of /8 Aurigae 

 and \ Ursae Majoris, proving these stars to be 

 binaries, which, however, are far beyond the 

 limits of resolving power of the largest telescopes. 

 Mention should also be made of the discovery of 

 the presence of bright hydrogen lines as a charac- 

 teristic feature of variable stars of Secchi's third 

 type, leading to the detection of a large number 

 of variables of this class ; and also of the interest- 

 ing series of lines in the spectrum of \ Puppis, 

 which have since become of considerable import- 

 ance in connection with theories of spectra. 



Pickering was not alone a zealous worker 

 himself ; he was ever ready to aid the work of 

 other institutions and individuals by advance 

 copies of data which might be of use to them, 

 by the loan of photographs, or in numberless 

 NO. 2576, VOL. 103] 



other ways. Besides the voluminous publications 

 of the observatory, he maintained a valuabk 

 service of bulletins and telegrams for the distribu- 

 tion of information respecting discoveries, made 

 at Harvard or elsewhere, which required imme- 

 diate announcement. 



The value of Pickering's contributions to science 

 was universally recognised. He was a foreign 

 member of the Royal Society, of the Institute of 

 France, and pf most of the other important learned 

 societies of Europe. The gold medal of the 

 Royal Astronomical Society was awarded to him 

 in 1886 for his photometric researches, and again 

 in 1901 for his researches on variable stars and 

 his work in astronomical photography. He was 

 president of the Astronomical Society of America, 

 and received the Bruce, Draper, and Rumford 

 medals. Honours were also bestowed upon him 

 by his own and other universities. 



LT.-COL. W. WATSON, C.M.G., F.R.S. 



BRITISH science is the poorer as the result of 

 the war by many a distinguished name. Few 

 have deserved more highly of their country, or 

 done more useful work in defending our men 

 against the scientific savagery of poison-gas 

 shells, than Lt.-Gol. William Watson as 

 director of the Central Laboratory, B.E.F., from 

 its establishment in June, 191 5, soon after the first 

 gas-attack, to the conclusion of 1918. The 

 hazardous and exacting nature of this work, in 

 the course of which Watson was frequently 

 "gassed," no doubt largely contributed to his 

 death, which took place, after two months in 

 hospital, on March 3, at the comparatively early 

 age of fifty. The full record of the manifold 

 activities of the Central Laboratory under his 

 direction will doubtless appear in its appropriate 

 place when further details are available. We must 

 be content here with a summary of his career as 

 a scientific investigator. 



Watson received his training, in the accurate 

 and delicate physical manipulation which distin- 

 guished all his work, at the Royal College of 

 Science under Sir Arthur Riicker and Prof. Boys, 

 and took his B.Sc, degree in 1890, securing first 

 place on the list of honours in physics. He 

 obtained an immediate appointment as demon- 

 strator in the college, and afterwards succeeded 

 to the assistant professorship in 1897. He was 

 elected a fellow of the Royal Society in 1901, and 

 became in due course one of the professors of 

 physics at the Imperial College of Science and 

 Technology. 



W^atson's first scientific work was as assistant in 

 the great magnetic survey of the British Isles insti- 

 tuted by RQcker and Thorpe, 1890-95, in which he 

 did the lion's share of the obser\ational work, and 

 appears in the record as the most accurate of the 

 observers. He also had the advantage of assist- 

 ing Prof. Boys in his delicate experiments with 

 the radio-micrometer, in timing the periodicity of 

 the electric discharge, and in photographing the 

 flight of bullets. In the meantime he was occu- 



