138 



NA TURE 



[June ii, 1891 



hydrogen over zinc heated to whiteness in a porcelain tube in a 

 Schliising furnace. When the tube, which is allowed to cool in 

 the stream of gas, is broken, immediately beyond the portion 

 which has been heated in the furnace a beautiful sublimate of 

 crystals of wurtzite is found. They consist of well-developed 

 hexagonal prisms, somewhat transparent and of a yellow colour, 

 exhibiting, according to Prof, Groth, their hemimorphic nature 

 in a most decided manner. In a similar way also Dr. Lorenz 

 has artificially prepared greenockite, sulphide of cadmium, 

 CdS. This synthesis is perhaps the easiest of all to effect, and 

 it may readily be conducted in an ordinary combustion-tube. 

 The metallic cadmium is placed in a porcelain boat, and com- 

 mences to react with the sulphuretted hydrogen at a temperature 

 just below its boiling-point. As soon as this temperature is 

 attained, the porcelain boat and the portion of the tube beyond 

 it become covered with magnificent long yellow skewer-like 

 crystals of greenockite, which Prof. Groth finds to be of two 

 kinds, hexagonal prisms isomorphous with troilite and wurtzite, 

 and a new form of greenockite consisting of monoclinic crystals. 

 Dr. Lorenz has further artificially prepared millerite, the sulphide 

 of nickel, NiS, by the same method, obtaining in this case very 

 minute but undoubtedly hexagonal crystals isomorphous with 

 the three other sulphides above described. 



The additions to the Zoological Society's Gardens during the 

 past week include a Macaque Monkey [Macacus cynomolgus ? ) 

 from India, presented by Mr. Walter Fraser ; a Rhesus Monkey 

 {Macacus rhesus 9 ) from India, presented by Colonel Beresford ; 

 a Great Black-headed Gull [Larus ichthyactus) from the Persian 

 Gulf, four Macqueen's Bustards {Houbara macqueeni cj <J ? 9 ) 

 from Western Asia, three Chaplin Crows {Corvus capellanus) 

 from Persia, presented by Mr. B. T. Ffinch, C.M.Z.S. ; a 

 Diamond Snake {Morelia spilotes) from New South Wales, 

 presented by Mr. J. Hellberg ; a Common Viper ( Vipcra berus) 

 from Hampshire, presented by Mr. W. H. B. Pain ; two 

 Piapecs (Plilosiovius senegalensis) from West Africa, purchased ; 

 a Collared Fruit Bat {Cynonycteris coUaris), four North African 

 Jackals {Canis anthus), two Partridge Bronze-wing Pigeons 

 {Geophaps scripta), bred in the Gardens. 



OUR ASTRONOMICAL COLUMN. 

 The Spectra of Double Stars.— A note on " The Dis- 

 covery of Double Stars by means of their Spectra" is contributed 

 by Prof.E. C. ?'icke:x\ngio Astronotnische Nachrichten, No. 3034. 

 When the components of a close binary system have similar 

 spectra, relative orbital motion in the line of sight may cause a 

 periodic doubling of the lines. But if the spectra be not similar 

 any lines common to both ought to be conspicuously strong, and, 

 provided the components have not equal and opposite velocities in 

 the line of sight, ought also to be displaced with reference to 

 other lines. Thus, if one component of a close binary system 

 has a Group V. spectrum, like our sun, and the other a Group 

 IV. spectrum, in which strongly marked hydrogen Imes is the 

 main feature, the resulting spectrum will have a composite 

 character, and careful meaburements should show that the position 

 of the hydrogen line is periodically displaced when compared 

 with the lines characteristic of the solar-type spectrum, o Canis 

 Majoris is the brightest star having this composite spectrum, and 

 the wave-length of the hydrogen line G, derived from a com- 

 parison with three lines of greater and three lines of smaller 

 wave-length, was 434 "09, which exceeds that derived from the 

 solar spectrum by 003. Similar measures of the hydrogen line 

 h gave a wave-length of 410-22, which also exceeds that in the 

 solar spectrum by 0-03. From this displacement it would 

 appear that if the phenomenon is due to the relative motion of a 

 faint component, it is receding at the rate of 20 kil metres per 

 second, as compared with the bright component. An examina- 

 tion shows that the following stars have the composite spectrum 

 referred to : 7 Andromedse, H.P. 650, e Bootis, a Scorpii, and 

 ^ Cygni, all of which are known to be double ; also ir Persei, 

 C Aurigae, 8 Sagittarii, 31 Cygni, and /3 Capricorni. In the 

 cases of the last two, the spectra of the distant companions are 



NO. I 128, VOL. 44] 



distinctly separated from those of the chief stars. Although the 

 strong hydrogen lines in the spectra investigated may be due to 

 the presence of a faint companion, their intensity may also be 

 due to many other causes. Thus, the strong hydrogen lines in 

 the solar spectrum are not due to the integration of the spectrum 

 of the sun and that of a companion. It is necessary, therefore, 

 to determine whether the displacement is subject to a periodic 

 variation or not, in order to test this method of discovering close 

 binaries. 



The Perseid Radiant. — At the St. Petersburg Academy 

 of -Sciences, on April 22, M. Bredichm concluded, from the 

 meteor observations made at Puikova by ten astronomers in 

 August 1890, " le courant des aerolithes n'est pas delimite par 

 un point ou un petit rond, mais presente une surface considerable 

 parsemee de radiants." 



THE FLORA OF DIAMOND ISLAND. 



"TJIAMOND ISLAND is situated at the mouth of theBassein 

 ^~^ River, in the Indian Ocean, about five miles from Pagoda 

 Point and eight miles from Cape Negrais, and in about 16° N. 

 lat. It is of sandstone formation, somewhat exceeds a square 

 mile in area, being about twice as long as broad, and the central 

 part is a kind of plateau 60 feet or so above the level of the 

 sea. W^ith the exception of a small clearing for a telegraph 

 station, the island is densely wooded down to the sea, but there 

 is no mangrove belt on any part of the sandy coast, unless it 

 be considered as represented by a few patches of Avicennia 

 officinalis. Thus is the island described, though in greater 

 detail, by Dr. D. Prain, Curator of the Herbarium of the Royal 

 Botanic Garden, Calcutta, who has visited the island in H.M. 

 Indian Marine Survey steamer Investigator, commanded by R. 

 F. Hoskyn, R.N. Dr. Prain has published an elaborate ana- 

 lytical account of the flora in the Journal of the Asiatic Society 

 of Bengal. He collected eighty-six species of flowering plants, 

 three ferns, and four funguses, among which there was not a 

 single novelty. The enumeration includes a number of culti- 

 vated plants, among them the coco-nut palm ; bat these are all of 

 recent introduction. It is supposed that the island was not pre- 

 viously inhabited, and therefore that the vegetation of the dense 

 wood overspreading the island is quite natural. The most in- 

 teresting fact brought out is the evident affinity with the some- 

 what distant Andaman flora, pointing to a former connection. 

 The Report is also valuable to the student of plant-distribution 

 for the details it contains of the habitats and relative frequency 

 of the component species of the vegetation. 



W. Botting Hemsley. 



UNI VERS I TV AND ED UCA TIONAL 

 INTELLIGENCE. 



Cambridge.— Lord Walsingham, F.R.S.,the High Steward 

 elect, has issued a letter of thanks to the Senate, in which he 

 promises to maintain the highest traditions of "our beloved 

 University." 



W. M. Hicks, F.R.S., late Fellow of St. John's College, and 

 Principal of Firth College, Sheffield, has been approved for the 

 degree of Doctor in Science. Dr. Hicks is the author of many 

 important memoirs in mathematical physics, and of an approved 

 text-book of dynamics. 



Prof. Newton has been appointed a Manager of the Balfour 

 Studentship Fund for five years. 



A. H. L. Newstead, Scholar of Christ's, and E. W. Mac- 

 Bride, Scholar of St. John's, and President of the Union Society, 

 have been nominated for research work at the Naples Zoological 

 Station. 



The Syndicate appointed for the purpose have selected a site 

 for the Sedgwick Memorial Museum on the old Botanic Garden 

 area, with a frontage to Downing Street. The proposed Museum 

 will lie between the new Chemical Laboratory and the old 

 Anatomical School, and complete one quadrangle of the new 

 Museums group. 



The following distinguished persons are proposed recipients 

 of honorary degrees on June 16 : — Lord Walsingham, F.R.S., 

 the Marquis of Dufferin and Ava, K.P., G.C.B., Prof. Rudolf 

 von Gneist, of Berlin, Sir Alfred Lyall, K.C.B., Sir Archibald 

 Geikie, F.R.S., Antonin Dvorak, Prof. Karl Weierstrass, of 

 Berlin, A. H. Taine, member of the French Academy, Dr. 



