June 12, 1890] 



NA TURE 



161 



reasonable and often correctly applied Scotch vei diet of "not 

 proven." 



In the annual address, delivered lately by Colonel J. Water- 

 house, President of ihe Asiatic Society of Bengal, and now printed, 

 he speaks highly of the work done by Indian museums and kindred 

 institutions. lie says they are exerting "a great educational 

 influence " on "the teeming masses " of India. Native visitors 

 are beginning " to take a really intelligent interest in the collec- 

 tions." Colonel Waterhouse urgts that the work of local 

 museums should be confined to the illustration of local products. 

 If objects from other districts are admitted, the name of their 

 place of origin should, he thinks, be distinctly marked upon 

 them, and they should be kept apart from the local collections. 



The U.S. Department of Agriculture has issued an elaborate 

 Report on the English sparrow (Passer domesticus) in North 

 America. The Report has been prepared, under the direction 

 of Dr. C. Hart Merriam, ornithologist to the Department, by 

 Mr. Walter B. Barrows, assistant ornithologist. Dr. Merriam 

 claims that it is "the most systematic, comprehensive, and im- 

 portant treatise ever published upon the economic relations of 

 any bird." The new immigrant into the United States is 

 accused of an enormous number of offences ; and no one who 

 studies the evidence brought together in this Report will be dis- 

 posed to say that his evil deeds have been exaggerated. The 

 climatic and other conditions of America have suited the sparrow 

 to perfection, and he has exercised freely all his powers of doing 

 mischief. The evidence set forth relates to the importation, 

 spread, increase, and checks on the increase of the bird ; the 

 injury done by him to birds, blossoms, and foliage ; the injury 

 to fruits, garden-seeds, and vegetables ; the injury to grain ; and 

 the relations of the sparrow to other birds, and to insects. All 

 sorts of suggestions for the destruction or abatement of the 

 nuisance are carefully considered. There is also interesting 

 evidence as to the sparrow in Europe and Australia. 



A PAPER upon the atomic weight of magnesium and the 

 properties of the pure metal obtained by distillation iti vacuo is 

 communicated to the current number of the Atttcrican Chemical 

 Jotirnal by Messrs. Burton and Vorce, of Cleveland, U.S. 

 When an attempt is made to distil magnesium in an ordinary 

 hard potash glass tube it is found that the vapour of the iretal 

 attacks the glass in a remarkable manner, a black voluminous 

 substance being formed which evolves a spontaneously inflam- 

 mable gas on treatment with an acid. This black substance is, 

 in fact, magnesium silicide, MgjSi, and the explosive gas silicon 

 tetrahydride, SiH4. When the silicide is brought in contact 

 with dilute acid there remains, after the liberation of silicon 

 hydride and conversion of the magnesium into a salt of the acid 

 employed, a quantity of a yellow substance which possesses the 

 properties of the lower oxide of silicon described by Mabery. 

 Hence it is not possible to use tubes entirely of glass for the 

 distillation of magnesium. But by lining the interior of the 

 heated portion of the tube with an inner tube of thin sheet-iron, 

 magnesium not alloying with iron, the distillation can be con- 

 ducted with perfect safety. The magnesium was packed in the 

 iron tube in the form of small pieces of ribbon, and the iron tube 

 then placed in an outer glass tube closed at one end and about 

 twice the length of the iron tube. The other end was afterwards 

 drawn out and connected with a Sprengel pump, and the tube 

 exhausted. The apparatus was then laid in a combustion furnace 

 and the tube heated, the closed end near which the iron tube and 

 its magnesium contents had been placed being heated much[more 

 strongly than the end nearest the pump. When the iron tube 

 became heated to bright redness the magnesium commenced to 

 volatilize and sublime into the relatively cooler portion, forming 

 at first a black mirror of silicide upon the glass, which protected 

 t from further corrosion. After continuing the heating for about 

 NO. 1076, VOL. 42] 



an hour in the case of the distillation of about ten grams of 

 metal, the gas was shut ofT, and the whole allowed to cool very 

 slowly so as to prevent fracture of the glass, the vacuum being 

 maintained as perfect as possible until quite cold. The distilled 

 magnesium was similarly redistilled three times, the product of 

 the fourth distillation alone, in which no traces of impurities 

 could be detected by analysis, being employed in the atomic 

 weight determinations. The magnesium was generally deposited 

 in the form of a thin crystalline bar of pure white metal which 

 readily separated from the coating of silicide, but in certain of 

 the distillations beautiful isolated crystals of considerable size 

 were formed. Weighed portions of the metal thus purified were 

 converted to the nitrate by means of purified nitric acid diluted 

 with wafer also specially purified and recently redistilled in a 

 platinum apparatus. The nitrate was then ignited to oxide, first 

 over a sand-bath, and finally to constant weight at the highest 

 temperature of a mufBe furnace. From the relation between the 

 weights of metal taken and oxide produced in ten experiments, 

 the mean value of the atomic weight of magnesium if O = i6 

 was found to be 24*287; if O = I5"95, Mg = 24-211. The 

 highest value found when O = 16 was 24 304, and the lowest 

 24"27l. The crystals of magnesium obtained during the distil- 

 lation were very perfect hexagonal prisms showing no planes but 

 those of the primary prism 00 P, primary pyramid P, and basal 

 plane oP. From measurements of the angles the axial ratio 

 a : c = \ : I "6202, which agrees tolerably well with the ratio 

 given by Des Cloizeaux from the measurement of crystals ob- 

 tained by Dumas in 1880. Magnesium is therefore isomorphous 

 with zinc and beryllium, which latter metal it very closely 

 resembles in its angular measurements and the ratio of its 

 axes. In case of Zn, a : t: = l : l "3564, and for beryllium, 

 a : c ~ \ : \ '5802. 



The additions to the Zoological Society's Gardens during the 

 past week include two Oak Dormice (Myoxus dryas), Central 

 European, presented by Lieut. -Colonel G. M. Cardew ; a 

 Vulpine Phalanger {Phalangista vulpina S ) from Australia, 

 presented by Mrs. Waterson ; a Silver-backed Fox (Cants 

 chama i ) from South Africa, presented by Captain H. D. 

 Travers, R.M.S. Tartar; a Great Kangaroo (Macropus gigan- 

 ieus ? ) from Australia, presented by Mr. Henry Irving, F.Z.S. ; 

 a Ring-necked VtnTxakttt {Pahcornis torquattts i) from India, 

 presented by Mr. Arthur O. Cooke ; a West African Love Bird 

 (Agapornis pidlaria) from West Africa, presented by Mrs. 

 Fell; a Chinese Bulbul (Pycnonottis sinensis) from China, pre- 

 sented by Lieut. -General Sir H. B. Lumsden, K.C.S.I., F.Z.S. . 

 three Common Peafowl (Pavo cristatus <J ? et juv.) from India 

 presented by Mrs, Francis Leighton ; a Common Kestrel 

 (Tinnunculus alaudarius), British, presented by Mr. C. 

 Ashdown, F. Z. S. ; a Loggerhead Turtle ( Thalassochelys caonana) 

 from the Atlantic Ocean, presented by Miss Beatrice Fort ; a 

 Grey Monitor { Varanus griseus) from the Sahara Desert, pre 

 sented by Dr. John Murray ; a Hawk-headed Parrot (Deroptytis 

 accipitrinus) from Brazil, deposited ; a Vociferous Sea Eagle 

 (Haliaclits vocifcr) from West Africa, a Red- crowned Pigeon 

 (Eryt/ircctias pukherrimd) from the Seychelles, purchased ; a 

 Japanese Deer (Cerz'its sika i), two Bennett's Wallabys 

 (Halmaturus bennetti cJ d ), a Vulpine Phalanger (Phalangista 

 vulpina d ), a Peacock Pheasant (Polyplectron chinquis), a 

 Swinhoe's Pheasant (Euplocamtis szvinhoii), four Spanish Blue 

 Magpies (Cyanopolius cooki), bred in the Gardens. 



OUR ASTRONOMICAL COLUMN. 

 Objects for the Spectroscope. 

 Sidereal Time at Greenwich at 10 p.m. on June 12 

 I5h. 24m. 22s. 



