QCTOBER 27, 1892] 



NATURE 



619 



[per calorie, or 4'l857 x lo'^ ergs. For the normal scale of the 

 hydrogen thermometer this would be 426 "84. 



A NEW and very convenient method of preparing acetylene 

 gas is described by M. Maquenne in the current number of the 

 Comptes Rendus. A short time ago the same chemist suc- 

 ceeded in preparing a comparatively stable compound of carbon 

 with the metal barium, BaCj, by heating powdered retort- 

 charcoal with barium amalgam in a current of hydrogen. Upon 

 bringing this compound in contact with water a violent action 

 was found to occur with evolution of almost pure acetylene 

 t;as. On account, however, of the troublesome nature of the 

 operations of procuring barium amalgam and preparing from 

 it the new compound, together with the very small quantities of 

 the latter eventually obtained, this mode of preparing acetylene 

 Was only of theoretical interest, and not suitable as a laboratory 

 method of preparation. M. iMaquenne now describes a new 

 process for preparing barium carbide, by means of which large 

 quantities may very readily be procured in a few minutes, and 

 from which correspondingly large volumes of acetylene may be 

 derived. The principle of the method consists in reducing 

 barium carbonate by metallic magnesium in presence of carbon. 

 An intimate mixture is first made of barium carbonate prepared 

 by precipitation, powdered metallic magnesium, and calcined 

 retort-carbon. Convenient amounts are twenty-six grams of 

 barium carbonate, ten and a half grams of magnesium, and 

 four grams of charcoal. This mixture is then introduced into 

 an iron bottle of about seven hundred cubic centimetres 

 capacity, furnished with a tube, also of iron, thirty centimetres 

 long and two centimetres internal diameter. The iron bottle 

 is then heated in a gas furnace which has previously been raised 

 to a red heat. At the expiration of about four minutes an 

 energetic reaction occurs, accompanied by the projection of 

 brilliant sparks from the mouth of the tube. The apparatus 

 should then at once be removed from the furnace, the end of 

 the tube stopped, and the bottle and contents rapidly cooled 

 by the external application of cold water. The product may 

 then be extracted, when it is found to consist of a mixture of 

 magnesia with 38 per cent, of carbide of barium, a little excess 

 of carbon, and a trace of cyanide formed at the expense of the 

 atmospheric nitrogen. The reaction accords very closely with 

 the equation : — 



BaCOs + 3Mg -h C = BaCs + SMgO. 

 Carbide of barium may be preserved for an indefinite time in a 

 dry atmosphere. It is a grey, porous, and very friable substance. 

 When heated to redness in the air it burns with a vivid incan- 

 descence. It is also capable of combustion in chlorine, hydro- 

 chloric acid gas, and vapour of sulphur. In order to prepare 

 acetylene from it the powder is most conveniently placed in a 

 small flask fitted with a doubly-bored caoutchouc stopper, 

 carrying a dropping funnel containing water, and a delivery 

 tube. The moment water is allowed to drop the equivalent 

 quantity of acetylene gas is evolved in accordance with the 

 equation : — 



BaCs + 2H2O = Ba(OH)2 -f CaH^. 

 The delivery of the acetylene may be regulated with great 

 nicety by suitable adjustment of the stopcock of the dropping 

 funnel. The acetylene thus prepared possesses the further 

 advantage of being remarkably pure, containing 98 per cent, of 

 C2H2. It is interesting to learn that by allowing a stream of 

 this pure acetylene to pass through a long heated glass tube 

 for a few hours several grams of synthetical benzene have been 

 accumulated by M. Maquenne. 



The additions to the Zoological Society's Gardens during the 

 past week include a Macaque Monkey {Macacus cynomolgus 9 \ 

 from India, presented by Mr. W. F. Faulding ; a Buffon's 



NO. 1200. VOL. 46] 



Touracou {Corythaix buffoni) from West Africa, presented by 

 Mr. A. L. Jones; two Double-banded S&nA Gronse [Pterocles 

 bicinctus <J ? ) from Senegal, presented by Mr. H. H. Shariand. 

 F.Z.S. ; a Gannet {Sida bassana), British, presented by Dr. 

 Davis ; a Roseate Cockatoo {Cacatua roseicapilla), a King Par- 

 rakeet {Aprosmictus scapulattis 9 ) from Australia, presented by 

 Mrs. Addiscott ; four Alligators {Alligator mississippiensis) 

 from the Mississippi, presented by Mr. John Terry; two Thick- 

 billed Seed-eaters {Oryzoborus crassirosUis), a Tropical Seed 

 Finch {Oryzoborus torridus), a Saffron Finch {Scyzalis Jlaveola), 

 a Bluish Finch {Spermophila coerulescens) from South America, 

 a Pufif Adder ( Vipera arietans) from West Africa, deposited. 



OUR ASTRONOMICAL COLUMN. 



Comet Barnard (October 12).— An Astronomische Nach- 

 richten circular note gives the following elements and ephemeris, 

 computed from observations made on the 1 6th, I7tb, and i8th 

 of this month : — 



Elements. 

 T = 1892 Nov. 12745 Beriin M.T. 

 w = 168 49 



a = 220 50 

 i = 21 39 



log. q = o 03669 

 Ephemeris Berlin Midnight. 



1892. .^•^- ^«<='- Log'^- Br. 



h. m. Q , 



Oct. 25 ... 20 6-6 ... +7 47 



27 ... 13s - 6 51 ... 9-6825 ... 1-46 



29 ... 215 ... 5 52 



31 ••• 29-8 ... 4 51 ... 96609 ... 1-66 



Nov. 2 ... 387 ... 3 47 



4 ... 48-2 ... 2 40 ... 9-6377 ... 1-87J 



6 ... 20 583 ... I 29 



As the brightness at the time of discovery is taken as unity, it 

 will be noticed that the comet is quickly gaining in intensity, 

 the value for November 8 being 208 Br. Its position on the 

 31st lies in the southernmost part of the constellation of the 

 Dolphin, forming very nearly an equilateral triangle with 

 o Aquilse and /3 Delphini. 



Discovery of Three New Planets by Photography. — 

 M. Perrotin has communicated to the French Academy an 

 account of the discovery of three small planets by M. 

 Charlois, of the Nice Observatory, by the aid of photography. 

 The apparatus employed consisted of an Hermagis portrait lens 

 of 15 cm. aperture and 80 cm. focal length, mounted pro- 

 visionally on M. Loewy's equatorial coudL The instrument 

 was being employed for the photography of the region of the 

 ecliptic. With exposures ranging from two hours and a half to 

 three hours, the eight negatives obtained since September 12 

 cover a region 80° long and 10° broad, and show all the stars 

 visible through the 38 cm. refractor. A careful examination of 

 the plates reveals the presence of three unknown and eight 

 known planets. The former, now known under the names 

 1892, D, E, and F, are all of about the twelfth magnitude. 



RUTHERFURD MEASURES OF STARS ABOUT )3 CYGNI. — 

 Mr. Harold Jacoby, in No. 4 of the Contributions from the 

 Observatory of Columbia College, New York, presents us with 

 the reduced results of the measures of the plates containing 

 the group of stars surrounding /3 Cygni. The method of 

 measurement was exactly the same as that employed in the 

 case of the Pleiades plates, but that of reduction has received 

 some slight modification. For instance, the measures of the 

 eastern and western impressions have not been separately 

 dealt with, but their mean has been taken, and the reduction 

 continued, using this mean as a single observation. As the 

 accuracy of these measurements depend on the exactitude of 

 the scale value determinations to a very considerable extent, 

 it is satisfactory to hear that this value has remained mate- 

 rially the same for a very long period. The largest and 

 smallest values recorded in the Pleiades plates were 28"-oi67 

 and 28"'oo66, the mean value amounting to 28" -0124, and it ig 



