522 



NATURE 



[March 31, 1892 



periodical fluctuations of the curve are markedly inferior to other 

 andlargervariationsupon which they appear superposed. . .The 

 range included between these extremes amounts to two seconds, 

 and is altogether too large to be attributed either to personal 

 equation or to any instrumental origin." 



The Discovery of Neptune. — During a visit to England, 

 in 1876, Prof. Holden was frequently with Mr. Lassell, and he 

 then learned a circumstance connected with the discovery of 

 Neptune which is not without interest. Now that Adams and 

 Lassell are both gone. Prof. Holden has published the brief 

 notes he made at the time, as a contribution to the history of 

 the great discovery. It is well known that, in October 1845, 

 Adams submitted to the Astronomer- Royal his computations 

 indicating the existence of an unknown world beyond Uranus. 

 The work was shown i>> Dawes, and he was so much impressed 

 by it that he wrote to Lassell, asking him to search for Neptune 

 in the region designated by Adams. Had the discoverer of the 

 two inner and faint satellites of Uranus, and the satellite of 

 Neptune, directed his 2-foot reflector to this region, there is 

 little doubt but that the planet would have been picked up. 

 However, the Fates ordained otherwise : Lassell was confined 

 to his sofa by a sprained ankle, and, when he recovered, the 

 letter of Dawes, giving the predicted place of Neptune, could 

 not be found. It turned out to have been destroyed by a too- 

 zealous maid-servant. Thus, "by a set of curious chances," 

 the new planet was never looked for by the then most powerful 

 telescope and most skilful observer in England. It was not 

 until many months after the letter of Dawes to Lassell that the 

 planet was found by Galle and D' Arrest, near the position given 

 by Leverrier, 



Astronomy at the Paris Academy, March 21. — At the 

 meeting of the Paris Academy of Sciences, on March 21, M. 

 Lcewy presented a picture of the Orion Nebula obtained at 

 Toulouse Observatory, with an exposure of five hours, on Feb- 

 ruary 24, 25, and 26. 



M. Bigourdan observed Swift's comet on March 17, 18, 19, 

 and 20, and determined its position. He describes it as "a 

 bright nebulosity, 2' in diameter, without a tail, and with a 

 well-defined stellar nucleus, the light of which is comparable 

 with that of a star of the eighth or ninth magnitude." Den- 

 ning's comet was seen on March 19 and 20, and five observa- 

 tions of position were made. It is described as "a feeble 

 nebulosity without a tail, 25" to 30" in diameter, brighter to- 

 wards the centre, but without any apparent nucleus. Its light 

 was at the most equal to that of stars of magnitude 13." M. 

 Rayet observed Swift's comet on March 17 and 19, and esti- 

 mated that its nucleus was of the sixth or seventh magnitude. 



M. Terby, in a letter to M. Faye, claims priority for the idea 

 that solar spots and other disturbances on the sun exert an 

 influence on terrestrial magnetism and electricity which varies 

 according to the position of the phenomena with reference to 

 the sun's visible disk. In a paper presented to the Brussels 

 Academy in 1883, " On the Existence and Cause of a Monthly 

 Periodicity of Aurorae," he showed that the fluctuations in 

 frequency of auroras were connected with the period of the 

 sun's synodic rotation. Hence, some portions of the solar 

 surface seem more capable of exerting terrestrial influence than 

 others. 



Variability of Nebul.^j. — In Nature of January 14 

 (p. 261) some observations were described which seemed to 

 indicate that a nebula in R.A. 3h. 36m., Decl. 95° 2't, was 

 variable. Dr. Lewis Swift notes, in Astronomy and Astro- 

 physics, that he has again looked for the nebula, and on January 

 31 succeeded in getting two glimpses of it, using a power of 195. 

 Although Dr. Swift is not inclined to believe that the nebula is 

 variable, it is strange that he should at one time have picked up 

 the object whilst sweeping, and yet not be able to find it after- 

 wards, even with the most persistent searching. That Dr. Dreyer, 

 also, should have failed to see the nebula on several occasions, 

 although he knew where and what to' look for, is almost un- 

 accountable, if the brightness is uniform. It is to be regretted 

 that the illumination of the sky at Rochester, from the electric 

 lights, seems likely to prevent Dr. Swift from continuing his 

 search for nebulae. 



Solar Prominence Photography. — As the great spot- 

 group of February was again coming round the sun's east limb 

 on March 3, M. Deslandres observed over it a prominence. 

 He also photographed it, and, at the meeting of the Paris 



NO. I I 70, VOL. 45] 



Academy of March 14, communicated the results obtained. 

 The Fraunhofer lines H and K are very bright on the photo- 

 graphs, and the entire series of ultra-violet hydrogen lines are 

 plainly visible. Other lines are seen which have not previously 

 been recognized as chromosphere lines, viz. the magnesium 

 triplet about A 383, and lines at A\ 375 '93, 376 '14, and 368*53, 

 the origins of which are unknown. 



The Aurora Spectrum. — The aurora of February 13 was 

 seen at Chicago, and Prof. Hale made some observations of its 

 spectrum, using a small direct-vision spectroscope. A bright 

 band was made out in the red, near C, and another was identi- 

 fied as the characteristic aurora-line. A very faint line, broad 

 and hazy, appeared in the green, near the position of b, and a 

 faint one near F. 



THE PROPERTIES OF AMORPHOUS BORON. 

 nPHE properties of pUre amorphous boron form the subject of 

 a contribution to the current number of the Comptes rendus 

 by M. Moissan. In our chemical note of March 3 (p. 421), the 

 method was described by which M. Moissan has recently suc- 

 ceeded in preparing the amorphous form of boron in a state of 

 almost perfect purity. The method consisted in reducing an 

 excess of boric anhydride with powdered metallic magnesium, 

 and subsequently repeatedly extracting the soluble products by 

 acids. He now proceeds to describe the physical and che- 

 mical properties of the element as thus obtained. Pure amor- 

 phous boron is a fine chestnut-coloured powder, which may be 

 readily moulded into adhesive masses by pressure. Its density 

 is 2 "45. It is infusible, even at the temperature of the electric 

 arc. When heated in the air to a temperature in the neigh- 

 bourhood of 700°, it inflames, and burns with formation of 

 boric anhydride. If a small quantity is heated strongly in a 

 test-tube, and, while hot, thrown into the air, a host of brilliant 

 sparks are produced. When the powder is heated in a current 

 of oxygen it burns with an intensely luminous flame, which, 

 when the experiment is performed in a dark room, is observed 

 to possess a green tint. The rays emitted are almost devoid of 

 actinic power, the greater portion of the chemically active end 

 of the spectrum being wanting. Pure amorphous boron reacts in 

 a beautiful manner with sulphur at a temperature of about 610"^, 

 brilliant incandescence occurring with production of sulphide 

 of boron. This latter substance is decomposed by water with 

 liberation of sulphuretted hydrogen. Selenium reacts with 

 amorphous boron in an analogous manner at a higher tempera- 

 ture, but without incandescence, the selenide of boron produced 

 evolving hydrogen selenide when brought in contact with water. 

 Tellurium, however, may be fused in presence of boron without 

 any reaction occurring. 



When amorphous boron is heated in an atmosphere of 

 chlorine to 410°, combination accompanied by bright incan- 

 descence occurs with formation of chloride of boron, which, if 

 the experiment is performed in a suitable apparatus, distils over 

 into a receiver placed to intercept it. Bromine combines with 

 boron to form the liquid bromide of boron at a temperature ap- 

 proaching 700°, the reaction likewise being accompanied by 

 incandescence. Even bromine water attacks boron, although 

 slowly, at the ordinary temperature, and an aqueous solution of 

 bromine in potassium bromide attacks it rapidly. Iodine ap- 

 pears to be without action even at a red heat. Amorphous 

 boron only combines directly with nitrogen at a high tempera- 

 ture, mere traces of the nitride being produced at temperatures 

 below 900° when the powder is heated in a current of nitrogen ; 

 but at about 1200° combination rapidly occurs. The vapours of 

 phosphorus, arsenic, and antimony do not react at available 

 temperatures. When amorphous boron is heated in the electric 

 arc in an atmosphere of hydrogen, boride of carbon is formed 

 with a portion of the carbon of the poles. 



The behaviour of metals towards amorphous boron is some- 

 what singular. The alkali metals may actually be distilled over 

 the powder without any apparent trace of combination. Mag- 

 nesium, on the contrary, combines with boron to form a boride 

 at a low red heat. Iron and aluminium also form borides at a 

 red heat, and silver and platinum react with even greater 

 facility. 



Acids react with amorphous boron with considerable energy. 

 At 250° sulphuric acid is reduced to sulphur dioxide. Nitric 

 acid in small quantities produces incandescence. Phosphoric 

 anhydride is reduced at 800° to phosphorus. Arsenious and 



