28o 



NATURE 



[January 21, 1892 



atmosphere favours or hinders the work of bees. The summers 

 of 1889 and 1890 are cited as presenting a marked contrast with 

 regard to both beet-sugar and honey, in correspondence with 

 weather-conditions ; the earlier year was a highly prosperous 

 one, the latter quite the opposite. 



In the Report, just issued, of the U.S. Commission of Fish 

 and Fisheries, on the fisheries of the great American lakes in 

 1885, it is noted that in Lake Michigan there is no fishing 

 through the ice in the southern end of the lake, but that in the 

 northern end, especially in Green Bay and along the north 

 shore, this fishery is extensive. For twenty years it has given 

 employment to a very large number of men living in the neigh- 

 bourhood of Green Bay, and many fishermen from other locali- 

 ties have found work there during the winter months. During 

 the winter season the bay used to present greater activity than 

 the surrounding land, hundreds of shanties and temporary huts 

 being built for shelter. Dealers drove about from place to 

 place on the ice to purchase the catch, and merchants sent 

 waggons with provisions for the fishermen. At the height of 

 the season it was not uncommon for the fishermen to bring their 

 families out to the fishing quarters, where they would remain 

 for some weeks, all hands helping to keep the nets in repair. 

 For several years this fishery, owing to the diminished quantity 

 of white-fish, has been less extensive, and the fishermen engaged 

 in it at present generally live at home, owning a horse and 

 sleigh, which enable them to visit their nets daily. 



At a recent meeting of the Field Naturalists' Club of Victoria, 

 Baron von Mueller advocated strongly the protection of insecti- 

 vorous and native birds in the colony. He thought that this 

 object might be attained, not only by putting a comparatively 

 heavy tax upon guns and by more strictly enforcing the present 

 laws, but by the initiation of some scheme which would enlist 

 the sympathy and co-operation of all persons interested in the 

 subject. He suggested that a distinctive badge might be worn 

 by members if such a union were ever formed. 



The Academic Royale des Sciences, des Lettres, et des 

 Beaux Arts de Belgique has issued its Annuaire for 1892. It 

 contains, besides much information as to the organization and 

 activity of the Academy, biographical sketches of deceased 

 members, with remarkably good portraits. 



An interesting memoir is contributed by Dr. Merz, of Zurich, 

 to the current number of the Berichte, concerning the compound 

 of nitrogen and magnesium, generally known as magnesium 

 nitride, MgjNj. Magnesium, like boron, appears to possess 

 a somewhat powerful affinity for nitrogen. Some years ago 

 Deville and Caron, during their distillations of magnesium for 

 the purpose of obtaining the pure metal, observed the pre- 

 sence of small transpar ent crystals, containing only magnesium 

 and nitrogen, upon the surface of the distilled metal. More 

 recently, Briegleb and Geuther have shown that nitride of mag- 

 nesium in an amorphous form may be prepared by heating 

 magnesium filings in a porcelain boat placed within a porcelain 

 tube traversed by a stream of nitrogen. Dr. Merz now describes 

 two extremely simple methods of obtaining the nitride, suitable 

 for lecture demonstration, and also some further properties of 

 this interesting substande. A quantity of finely-powdered and 

 carefully dried magnesium, about two grams in weight, is placed 

 in a wide piece of combustion tubing about twenty centimetres 

 long, closed at one end. Attached to the open end of this tube 

 by means of a wide caoutchouc connection is a narrower tube 

 closed by a caoutchouc stopper, through which passes the nitrogen 

 delivery tube. A short side-tube blown upon the narrower tube 

 carrying the stopper serves for the exit of the gas, and is con- 

 nected by narrow caoutchouc tubing with a long vertical tube 

 bent round parallel to itself, the open end of which dips beneath 

 NO. II 60, VOL. 45] 



the surface of some coloured water. The air is first displaced 

 from the whole apparatus by means of pure dry nitrogen, and 

 when this is accomplished, the combustion tube containing the 

 magnesium, laid nearly horizontally, is heated by means of a triple 

 Bunsen burner. After two or three minutes have elapsed from 

 the attainment of a red heat, the speed of the current of nitrogen 

 may be slackened by means of a screw clip placed somewhere in 

 its path, when the coloured water will rapidly rise in the vertical 

 tube, attaining a height of ten feet, if the tube is so long, in a 

 couple of minutes, thus exhibiting in a graphic manner the rapid 

 absorption of the nitrogen by the magnesium. On allowing the 

 experiment to proceed for upwards of an hour, almost the whole 

 of the magnesium is converted to nitride, the small remainder 

 reacting with the glass, and producing a black mirror of silicon. 

 Magnesium nitride obtained by this method is a light, volumin- 

 ous, friable, and yellowish-gray-coloured substance when cold, 

 but reddish-brown while hot. When exposed to the air, it 

 smells strongly of ammonia, owing to its decomposition by the 

 moisture present. When a little water is poured upon it, great 

 rise of temperature occurs, together with hissing, increase in 

 volume, and evolution of steam, just as when quicklime is slaked. 

 Ammonia is also evolved in large quantities, and white mag- 

 nesium hydrate remains. The decomposition by means of water 

 is most effective when performed at the bottom of a large flask, 

 which rapidly becomes filled with ammonia gas ; the moment a 

 little hydrochloric acid is introduced upon a feather or other 

 convenient carrier, the flask becomes filled with dense fumes of 

 ammonium chloride. Dr. Merz further shows that the nitride 

 may likewise be obtained by heating magnesium in a current of 

 dry ammonia to a temperature considerably lower than that 

 which is required in the case of free nitrogen, and very much 

 lower than that employed by Briegleb and Geuther in some 

 similar experiments made by them. As soon as this temperature 

 is attained, a brilliant incandescence occurs, and the flame may 

 be removed ; hydrogen is evolved in a rapid stream, and 95 per 

 cent, of the magnesium is converted in three or four minutes to 

 nitride. 



The additions to the Zoological Society's Gardens during the 

 past week include a Green Monkey {Cercopithecus callitrichus i ), 

 a Sooty Mangabey {Cercocebus fuliginosus ? ) from West Africa, 

 presented by Canon Taylor Smith ; a Moustache Monkey 

 {Cercopithecus cephus i) from West Africa, presented by Mr. 

 Alfred Lloyd ; a Silver-backed Fox (Cants chama) from 

 Damaraland, South Africa, presented by Mr. E. Aubrey Hart ; 

 two Virginian Opossums [Didelphys virginiana) from North 

 America, presented by Mr. John Brinsmead, F.Z.S. ; a Com- 

 mon Jay [Garruhis glandarms), British, presented by Mr. 

 Charles Faulkner; a Great Titmouse (Parus major), a Coal 

 Titmouse {Parus ater), a Blue Titmouse {Parus cisruleus), 

 British, presented by Captain Salvin ; a Bonham's Partridge 

 {Ammope^-dix bonhami) from Western Asia, deposited ; a 

 Bronze-winged Pigeon {Phaps chalcoptera ? ) from Australia, 

 purchased. 



OUR ASTRONOMICAL COLUMN. 



Motion of Stars in the Line of Sight.— Prof. H. C. 

 Vogel, in Monthly Notices K.A.S. for December 1891, fully 

 describes the method used at Potsdam for determining the 

 velocity of stars in the line of sight, and states the chief results 

 that have been obtained since the work was begun in 1887. In 

 order to insure great stability with the smallest poi^sible weight, 

 the frame of the spectroscope is made of cast steel. The camera 

 is also constructed of steel, and the dark slides are of brass. It 

 may be worth remarking, however, in this connection, that sta- 

 bility would have been secured if aluminium had been used 

 instead of steel and brass, and this with a little more than one- 

 third the weight. A spectroscope similar to Prof. Vogel's, but 



