October 31, 1895] 



AM TURE 



65; 



C. Martin ; two Hybrid Widgeons [hcWSKiiM Mama l>£iulofe^\\A 

 Anas boschas), bred in England, presented by Mr. VVellesley 

 Taylor; a Cape Viper (Cansiis rhomliealns), two Kufescent 

 Snakes (Leptodira rii/esieits) from South Africa, presented by 

 Mr. y. E. Matcham ; a Great Kangaroo (Macropiis giganleus) 

 from Australia, deposited ; two Hunter's S])iny Mice (Acomys 

 htinieri), born in the Ciardens. 



OUR ASTRONOMICAL COLUMN. 



RuTHERKURiVs Stki.i..\r Photograi'HS. — The pioneer 

 work of the late Dr. Rutherfurd in photographic star charting 

 i.s gradually assuming a form which gives the results a high 

 scientific value. In 1890, Dr. Kulherfurd presented his original 

 negatives, many of them taken more than twenty years ago, ti^ 

 the Columbia College ()b.servatory. New- \'ork, together with 

 some thirty volumes of measures of certain star photographs, 

 and Prof. J. R. Rees was authorised to arrange for the discussion 

 of the photographs. After Dr. Rutherfurd's death in 1S92, his 

 son, Rutherfurd Stuyvesant, generously provided funds for con- 

 tinuing the rechiction and publication of the measures. The 

 results obtained for the stars of the Pleiades group, and for the 

 stars about J3 C)gni have already been published, as well as an 

 investigation of the parallaxes of p. and 9 Cassiopei;v. To these 

 are now added two papers giving full details of an .'avestigation 

 of the parallax of tj CassiopciLV, and of the reduction of positions 

 of sixt)-two stars in the neighbourhood (Ann. AV«' Yorl; Acad. 

 Sri., vol. viii. 301, 381). Using three pairs of comparison stars, 

 the i^arallax deduced for tj Cassioi>ei.v- is o"'443 i o '043 » Ofi 

 taking six pairs, o""465 ± o"'044 (see Nati're, vol. Hi. 

 p. 61). In view of the difficulty of getting comparison stars 

 .suitably situated either with respect to position angle, or 

 distance, it was considered desirable to take a larger number 

 than usual, and hence six pairs were reduced, being all that were 

 sufficiently impressed on the plates in both seasons of the year. 

 Only the three jiairs wliich lead to the first-named value, 

 however, are so situated with reference to the parallactic ellipse 

 as to give good coefficients for the parallax. 



Radiai, Vei.ocitif.s or Satikn. — The recent spectroscopic 

 investigations of the velocities in the Saturnian system furnish an 

 admirable illustration of the accuracy at present attainable in 

 this department of astronomical research. Prof. Keeler, M. 

 Deslandres, Prof. Campbell, and Dr. Belopolsky ha\e each in 

 turn directed their attention to the planet, and the following 

 table brings together the ditVerent results obtained, and compares 

 them with the computed velocities : — ■ 



It thus appears that in the hands of competent observers, the 

 jihotographic methods now emplojed for the determination of 

 velocities along the line of sight may Ix; relied upon to give 

 values which are correct to within one kilometre per second : 

 while for results depending upon the measurement of more than 

 one velocit)', a little greater latitude must be allowed. 



In reply to the objection of M. Deslandres and Prof. .Seeliger, 

 that the spectroscopic results do not strictly ptove the mcteoritic 

 constitution of the ring, I'rof. Keeler has pointed out that any 

 other explanatifin which is consistent with them can onl)' be re- 

 garded as artificial, or inherently improbable (.-/r/. Nacli. 3313). 

 If the ring were composed of concentric solid rings, a line in 

 the spectrum would be made up of short straight lines, like an end 

 view of a Hight of stairs. I'rof Keeler does not consider his own 

 photographs capable of showing more than ten such subdivi- 

 sions, for if the number were greater than this, the step-like 

 structure of the lines would be destroyed by unavoidable errors 

 in guiding : but up to a certain point the effect would still be 

 apparent in the w idening of the lines. He finds, however, that 

 the definition of the lines in the spectrum of the ring is less 

 affected by guiding errors than that of the lines of the planet, as 

 might be expected if the lines w ere smooth curves such as would 

 be produced in the case of a ineteoritic ring. 



NO. 1357, VOL. 52] 



The Cape OiiSERVAiORV.— Dr. Gill's rc-jxirt of the work 

 done at the Cape Obser\'atory during 1894 has Ijeen distributed. 

 It opens by pointing out that the chief desideratum in a.stronomy 

 during the past decade has been an adequate provision for the 

 study of astrophysics in the southern hemisphere. As the 

 readers of Nature are aware, Mr. Prank McClean, F.R.S., 

 has given to the Cape Observatory a splendid equipment for 

 such work, so the need has been met, and a harvest of results 

 may be looked for as soon as the instrument is erected. With 

 reference to this generous gift, the report says that the telescope 

 will have a photographic object-glass of 24 inches aperture and 

 22A feet focal length, and be provided with an objective 

 prism of the same aperture having a refracting angle of 7^°. 

 Mounted parallel to this there will be a visual telescope of 18 

 inches aperture and of the same focal length as the photographic 

 telescope. The equatorial mounting will have complete circum- 

 polar motion for within 30' of the zenith ; and w ill be sufficiently 

 elevated to allow of a slit spectroscope suitable for determining 

 motion in the line of sight. Such a sijectroscope will also be 

 provided by .Mr. McClean, together with an observatory of light 

 construction. The instrument has been for some time under 

 construction by Sir Howard Grubb, and will probably be com- 

 pleted before the end of 1896. 



Among the work done with the astro-photographic telescope, 

 wc notice that, after rejecting all plates of insufficient exposure, 

 or which are otherwise faulty, only 70 of the plates for the 

 Catalogue, out of 1632 areas assigned to the Cape, remain to be 

 done. Of the chart plates, 263 have been passed as satisfactory. 

 Measures of the diameters of the photographic discs of a 

 variable star in Vela, together with those of nine comparison 

 stars, prove the former to be a variable of the Algol type, its 

 period being about 5d. 22h. 24m. 4s. A complete discussion of 

 the light curve and period will shortly be undertaken. 



The researches on the solar parallax have been carried 

 forward, three sections of the work, on the observations of the 

 minor planets X'ictoria and Sappho, having been pa,ssed through 

 the press. The manuscript of the definitive discussion of the 

 observations of \ ictoria has l^een sent to the printers ; while the 

 computatiims of the solar [xirallax from the observations of 

 .Sappho and Dr. Elkins reductions of the observations of Iris 

 are completed. 



THE 



LXSTITUTION OF MECHANICAL 

 ENGINEERS. 



A' 



N ordinary general meeting of the Institution of Mechanical 

 Engineers was held on the evenings of Wednesday and 

 Thursday, October 23 and 24, at the Royal United Service 

 Institution, Whitehall, the Council having lent their new 

 theatre for the purpose. The building of the Institution of 

 Civil Engineers, where the Mechanical Engineers have held 

 their London meetings for years, is now in process of re- 

 building. It is to be hoped, however, that the Institution of 

 Mechanical I'^ngineers will, before long, have their own 

 premises. 



There were three papers down for reading on the first day of 

 the meeting : — 



" The Electric Lighting of Edinbui^h," by Henr\ |. 

 Burstall. 



" Reijort on the Lille Experiments uiwn the Efficiency of 

 Ropes and Belts for the Transmission of Power," translated 

 by Prof. David S. Cap|K»r. 



" Observations on the Lille Experiments up<m the Efficiency 

 of Ropes and Belts for the Transmission of Power," by I'rof. 

 Da\nd S. Capper. 



The chair was taken on each evening at 7.30, by Prof. 

 Alexander B. W. Kennedy, F. R.S. On the first evening 

 Mr. Burstall's pai>er was read and discussed. 



The electric lighting of lulinburgh is in the hands of the 

 Corporation. It was decided u])on in 1893, when the work of 

 designing and superintending the scheme was entrusted to Prof. 

 Kennedy, the President of the Institution. From an electrical 

 point of view the city consists of two districts. In one the 

 houses are close together, and the demand for light may be ex- 

 pected to be fairly concentrated ; in the other it will lie more 

 scattered. Having regard to the different districts to be served, 

 and taking into account all the local circumstances, it was deciiled, 

 after comparison of the various systems of supply and distribu- 

 tion which could be used, to adopt a low tension three-wire system 



