March 3, 1898] 



NATURE 



419 



At the meeting of the Vienna Academy' of 'Sciences, on 

 December i6 last, letter^ were read from Dr. Stemdachner, the 

 Director of the PoUi Expedition in the Red Sea. Writing 

 at the end of November, Dr. Steindachner reports ihat deep-sea 

 work wa:s at an end, but that observations along the coast, and 

 amongst the islands were being continned as the very unfavourable 

 weather permitted. Valuable fcoirections were made on the 

 Dahalak and Nakra Khor islands', specially in connection with 

 the coral formations and the shallow- water fishes ; and the 

 extinct volcanoes and the lava-sheets of Peacock Hill Bay were 

 examined. The Pola reached Assab on November 30, and 

 Mocha on December 14, 1897. 



M. LE Co.MTE P. DE Barthelemy publishes a letter in the 

 Comptes rendus of the Paris Geographical Society, on the 

 possible lines of communication between Luang-Prabang and 

 the coast, and on the navigability of the Mekong. It would 

 seem that little or nothing can be made of the Tran-Nunh 

 plains as long as they remain in the hands of the present 

 degenerate population ; although something might be possible if 

 the Meo population of the mountainous districts took their place. 

 The only part of the Mekong really adapted to navigation is 

 the stretch of 650 kilometres between Vien-Tiane and Savan- 

 nakhek. The future of Luang-Prabang evidently depends on 

 the speedy realisation of one or more of the numerous railway 

 schemes proposed. 



Mr. Porter has just published the tenth part of Messrs. 

 Sclater and Thomas's illustrated " Book of Antelopes." Two 

 more parts, already in a forward state, will finish the account 

 of the Gazelles and allied forms, and bring the third volume 

 to a close. The fourth and concluding volume will be 

 devoted to the Oryxes and Strepsiceres. Altogether the work 

 will contain one hundred coloured plates, about seventy of which 

 were originally prepared under the superintendence of the late 

 Sir Victor Brooke, many years ago, for a somewhat similar work 

 which he had planned, but did not live to accomplish. 



In referring to the election of three new members of the 

 Athenceum Club, in the first note last week, the designation of 

 the Club was inadvertently omitted. 



Dr. G. Linds.w Johnson writes calling attention to an 

 obvious misprint in the fortieth stereotyped edition of Vega's 

 Logarithmic Tables. The logarithmic sine of o^ 6', printed 

 as 9'24i877i, should be 7"24i877i. 



Prof. Charles Fabre, of the University of Toulouse, has 

 just completed the second supplement to his well-known treatise 

 on Photography. The new volume deals with the progress made 

 in all branches of the subject during the years 1893 to 1896. 



The additions to the Zoological Society's Gardens during the 

 past week include three Black-backed Jackals [Canis tnesomelas) 

 from South Africa, presented by Mr. J. E. Matcham ; a Black- 

 backed Jackal {Cants mesomelas) from South Africa, presented 

 by Captain Travers ; two Black Spider-Monkeys (Aides ater) 

 from Eastern Peru, a Downy Owl (Pulsatrix torquata) from 

 Para, twelve White's Tree Frogs (Hyla cartilea) from Australia, 

 deposited ; a Temminck's Tragopan {Ceriornis ietnmincki) from 

 China, a Bearded Lizard {Amphibolurus barbatus) from Aus- 

 tralia, purchased. 



OUR ASTRONOMICAL COLUMN. 



Eclipse Negatives. — In order to minimise the risk in re- 

 turning the eclipse negatives to England from the Eclipse 

 Station at Viziadrug, they were divided into three batches, a 

 complete set being made up in each batch by positives from the 

 other negatives. Two of these sets have already arrived safely 

 in England, and they testify to the clearness of the atmosphere 

 during totality. The smallness of the prominences is very 

 noticeable, both in hydrogen and K (calcium) radiations, a fact 



NO. 1479, VOL. 57] 



which was observed at South Kensington in H. light on the day 



of the eclipse. Another conspicuous feature is the intense 

 brightness of some of the coronal streamers at their base. The 

 negatives of the corona also verify the reports from the visual 

 observations, which stated that the general form was like those 

 of 1886 and 1896. The resemblance to the latter is very 

 striking, especially when we remember that it was the north- 

 point of the axis which was presented to us at that eclipse %■ 

 whilst in the last eclipse in January, the south point of the axis 

 is inclined towards us. 



Cinematograph in Astronomy. — We have already learnt 

 that the cinematograph was employed with success during the 

 recent solar eclipse, but M. Camille Flammarion has turned it 

 to the further use of exhibiting to a large audience the various 

 celestial movements. He has photographed the heavens at 

 different times from sunset to sunrise with a wide-angled lens xr* 

 the cinematograph, and as the whole movements during a single 

 night are projected on the screen, and passed through in a few 

 minutes, no very rapid rate of exposing the photographs is- 

 required. For showing sunset at one horizon, followed by the 

 movement of the stars and sunrise at the other horizon, and 

 also the movement of the moon amongst the stars, this method 

 has been employed with great success. He proposes in addition 

 to this to photograph the sun-spots, and thus exhibit by their 

 movement the rotation of the sun. For the earth he has con- 

 structed a large model, and photographed it with a cinemato- 

 graph when rotating and illuminated by light arranged so as to 

 represent the sun ; this was exhibited at the last meeting of the 

 French Astronomical Society, and was greatly admired. 



. A Probable New Star. — In Asir. Ncuh., No. 3476, it i* 

 pointed out that the probable new star announced by Espin, and 

 not in the B. D., is, however, in the small edition as an- 

 addendum, +32°-i526a; 8'omag., 7h. 12m. i5-6s.,-t-32° i8'-4L. 

 This is the same star as recorded by the Rev. T. E. Espin, so in 

 all probability it is another observation of a variable star. An- 

 examination of its spectrum, made at South Kensington, at once 

 showed that the star had not a spectrum peculiar to temporary 

 stars, and hence was probably only an omission from the star 

 charts. 



Electrolytic Reflectors. — In a paper read before the 

 Institution of Electrical Engineers, and reproduced in Industries 

 and Iron for February 18, Mr. Sherard Cowper-Coles de- 

 scribes a method by which a metallic reflector can be made by 

 an electrolytic process. The method is intended, in the first 

 place, for the manufacture of metallic mirrors for use as projectors 

 in search lights, and also to overcome the difficulty that has 

 been experienced in producing a true metallic reflector that will 

 not readily tarnish when exposed to the heat of an arc light ;. 

 but the same method is also applicable for the production of 

 mirrors for astronomical purposes. The process is, of course, a 

 copying one. and consists in taking a concave surface from a 

 convex mould, so figured as to give the correct curvature to the 

 copy taken from it. In the words of the author, "a glass mould 

 is prep^ired, the convex side of which is accurately shaped and 

 polished to form a true reflecting surface. On the prepared 

 surface is deposited a coating of metallic silver, which is thrown, 

 down chemically on the glass, and then polished so as to ensure 

 the copper backing being adherent to the silver. The mould 

 thus prepared is placed in a suitable ring and frame, and im- 

 mersed in an electrolyte of copper sulphate, the mould being 

 rotated in a horizontal position. The copper adheres firmly to- 

 the silver, and together they form the reflector, which is sub- 

 sequently separated from the glass mould by placing the whole 

 in cold or lukewarm water, and then gradually raising the tem- 

 perature of the water to 120'' F. , when the metal reflector will 

 leave the glass mould, due to the unequal expansion of the two." 

 The concave surface of the reflector thus obtained has a brilliant 

 polish, and requires no further treatment to answer all the pur- 

 poses of a reflector ; but for uses where tarnishing would soon 

 take place, it is further immersed in a bath of palladium am- 

 monium chloride, and a coating of palladium deposited on the 

 concave side ; this metal does not tarnish readily, and resists- 

 heat to a wonderful degree. 



This new method of making mirrors electrolytically would 

 seem to have a promising future before it, for great pains could 

 be taken in making the mould, from which any number of 

 copies could be taken without the usual laborious process of 

 grinding and figuring each individual mirror, and yet each one 

 would have a correct reflecting surface. 



