October 30, 1890] 



NATURE 



649 



have lost none of their value, notwithstanding subsequent ex- 

 ploration ; and the whole gives a vivid description of the explored 

 regian, from the Caspian Sea, over the Ust-Urt plateau, to 

 lie mouth of the Amu-daria and to Samarkand. Of the 

 many short notes scattered in the diary we may select 

 me in which it is mentioned that Barbot de Marny has 

 li.id the opportunity of finally ascertaining that the so- 

 ailed bugry of the Caspian shore are simply due to denuda- 

 ion. The layers of clay and sand of which they consist are 

 mostly horizontal, and, when they are not so, the strati- 

 cation has no relation whatever to the exterior shape 

 r these elongated low ridges. The next contribution to the 

 ime fascicule is by M. Andrusoff. It is full of geological data, 

 and its conclusions are very interesting, the author never failing 

 to discriminate between what is already proved and what still 

 belongs to the domain of hypothesis. His remarks about the 

 '"nspian Sea and its present fauna being remains of a Miocene 

 ca, and the enumeration of the geological problems in connec- 

 ion with that fact which remain yet unsettled, will be read by 

 xologists with interest, the more so as the substance of this 

 aper has been given in German in the Jahrbuck der k.k. 

 G eologischen Reichsanstalt, vol. xxxviii. 



The following are the arrangements for Tuesday evening 

 lectures at the Royal Victoria Hall during November :— Novem- 

 ber 4, Mr. Arnold Mitchell, " Old Buildings and the Story they 

 tell " ; November ii, Mr. A. H. Gilkes, " Columbus " ; Novem- 

 ber 18, Mr. A. P. Laurie, "Air and Water," with experiments; 

 November 25, Mr. Hilliard Atteridge, "The New Divisions of 

 Africa." The oxy hydrogen lantern will be used with all these 

 lectures. 



In our note on the Rev. J. A. Galbraith, on October 23, the 

 ast three lines should have been printed as follows : — " In 1854 

 he was chosen Erasmus Smith Professor of Experimental Philo- 

 sophy. Along with Dr. Haughton, Prof Galbraith was the 

 author of various excellent scientific manuals." 



In a communication to the cunent number of the Comptes 

 . cndus, M. Moissan announces the result of his redetermination 

 of the atomic weight of fluorine. The method adopted consisted 

 in converting a known weight of sodium, calcium, or barium 

 lluoride, prepared in a manner specially devised by M. Moissan 

 in order to exclude impurities, into sulphate by repeated ignition 

 with pure sulphuric acid in a small platinum retort. The 

 process for obtaining pure sodium fluoride was as follows. 

 An already fairly pure specimen of sodium chloride was freed 

 from the last traces of potassium by a large number of fractional 

 crystallizations. This was then converted into bicarbonate, of 

 soda by saturating its aqueous solution successively with am- 

 monium and carbon dioxide. The precipitated bicarbonate, after 

 repeated washing, was converted into the normal carbonate by 

 boiling its solution in water, and the crystals which separated 

 on evaporation were freed from traces of chloride by repeated 

 partial crystallization. The carbonate was next converted into 

 fluoride by treatment with redistilled hydrofluoric acid origin- 

 ally prepared by distillation of hydrogen potassium fluoride, 

 HF . KF. The sodium fluoride thus obtained, after ignition 

 at a red heat, was probably the purest specimen which has 

 ever been obtained. As the result of five ignitions with 

 sulphuric acid, the values obtained for the atomic weight of 

 tluorine ranged from I9'04 to l9'o8, when Na = 23*05 (Stas), 

 S = 32*07 (Stas), and O = 16. The calcium and barium 

 fluorides employed in the second and third series of deter- 

 minations were obtained in microscopic crystals by precipitating 

 potassium fluoride with calcium or barium chloride in dilute 

 solutions of particular strengths. The values obtained in the 

 case of four experiments with calcium fluoride varied from 19*02 

 to 1908, and as the result of five determinations with barium 

 NO. 1096, VOL. 42] 



fluoride, 19*05-19*09. As barium fluoride is not so regularly 

 decomposed by sulphuric acid as sodium and calcium fluorides, 

 M. Moissan considers that the nearest approximation to the 

 truth is aff^orded by taking the mean of the experiments with the 

 the two latter fluorides. This value is 19*05. Hence the atomic 

 weight of fluorine may be considered, as has previously been 

 supposed, to be practically represented by the whole number 19. 



The additions to the Zoological Society's Gardens during the 

 past week include a Diana 'MonVey [Cercopii/iecus diana 9 ) from 

 West Africa, presented by Mr, Howard V. Henry ; a Spotted 

 Ichneumon {Herpestes ncpalemis) from Nepal, presented by Mr. 

 J. Percy Leith, F.Z.S. ; a Polecat {MmUla putorius), British, 

 presented by Mr. F. D. Lea Smith ; two Laughing Kingfishers 

 {Dacelo gigantea) from Australia, presented by Mr. W. B. 

 Phillips ; two Pomatorhine Skuas {Stercorarius pomatorhinus), 

 British, presented by Mr. T. E. Gunn ; a Cashmere Monkey 

 {Macacus pelops ? ) from Cashmere, deposited ; two Common 

 Squirrels (Scitirus vulgaris), two Reed Buntings {Embet'iza 

 schceniclus), two Redpolls {Linota rufescens), British, purchated ; 

 an Angora Goat {Capra hircus 9 van), received in exchange; 

 two Vinaceous Turtle Doves {Tiirtur vinaceus), bred in the 

 Gardens. 



OUR ASTRONOMICAL COLUMN. 



Objects for the Spectroscope. 



Sidereal Time at Greenwich at 10 p.m. on October 30 = 

 oh. 36m. 39s. 



Remarks. 



(i) The spectrum of this bright nebula has not yet been 

 recorded. The G.C. description is: "Very bright; very 

 large ; much extended in the direction 165° ; very gradually 

 very much brighter in the middle." 



(2) This is the companion to the Great Nebula in Andromeda, 

 which is described "by Herschel as " exceptionally bright ; 

 large ; round ; pretty suddenly much brighter in the middle to 

 a nucleus." With reference to the spectrum, Dr. Huggins 

 notes: "This small but very bright companion of the Great 

 Nebula of Andromeda presents a spectrum exactly similar to 

 that of 31 M (the Great Nebula). The spectrum appears to end 

 abruptly in the orange, and throughout its length is not uniform, 

 but is evidently crossed either by lines of absorption or by bright 

 lines." Referring to the Great Nebula, the same observer 

 wrote: "The spectrum could be traced from about D to F. 

 The light appeared to cease very abruptly in the orange ; . . . 

 no indications of the bright lines." A comparison of the two 

 descriptions would lead one to suppose that the spectrum of the 

 companion is the more discontinuous of the two, and, if this be 

 the case, measurements of the positions of the brightnesses in 

 the spectrum may teach us a good deal about the nebulse which 

 have so-called " continuous '" spectra. After such a definite 

 statement by Dr. Huggins as to the existence cf irregularities, 

 it is highly desirable that further observations and measurements 

 should be made. Carbon comparisons (spirit-lamp flame) are 

 suggested. 



(3) A star of Group II., with bands 2, 3, 5, 7, 8 so narrow 

 that Duner describes them as "little more than lines." Narrow 

 bands are ccnimon to both the eaily and late species of the 



