August 2, 1894J 



NATURE 



327 



cotton at or near Manchester, in which city the Institution of 

 Mechanical Engineers is at present holding its summer meeting. 

 This section of the number is, in fact, specially designed for 

 the use of those who are taking part in the meeting of the 

 Institution. 



Part 2 of vol. xv. of the Journal of the Sanitary Institute 

 •contains, besides Proceedings of the Institute, notes on sanita- 

 tion abroad, Ac, an article by Dr. Louis Parkes, entitled "The 

 Possibility of the Spread of Disease through the River Waters 

 supplied to London," being a review of the evidence given by 

 the bacteriological witnesses before the Royal Commission on 

 Metropolitan Water Supply, 1893. 



The August number of Natural Science contains the follow- 

 ing articles: — "The Evolution of the Thames," Dr. J. W. 

 Gregory ; " Some Account of the Gall-making Insects of 

 Australia," W. W. Froggatt ; " Books of Reference in the 

 Natural Sciences," C. Davies Sherborn ; "Some Reforms in 

 the Oxford University Museum," E. S. Goodrich ; " Ilertwig's 

 ' Preformation or New Formation,'" P. Chalmers Mitchell ; and 

 a special illustrated supplement on " Taxidermy as a Fine Art." 

 The process illustrations in this supplement, and in t'..e article 

 by Mr. Goodrich, are for the most part very successful. 



The " Proceedings of the Physical Society of London," vol. 

 xii. part 4, has just been issued. 



The August part oi Science Gossip has a portrait of Dr. Ludwig 

 Mond, F. R. S., the munificent donor of the new laboratory for 

 physical and chemical research in connection with the Royal 

 Institution, to which we referred at length in our issue of July 5. 



Another remarkable nitrogen compound, nitramide 

 NOoNIL, is described in the current Beric/itehy its discoverers, 

 Drs. Thiele and Lachman, of Munich. A short time ago, these 

 chemists showed that by the action of sulphuric and nitric 

 acids upon urethane a nitro-derivative, nitrourethane 

 NOn . NHCOOC.jH., was produced. When this substance is 

 dissolved in water, and the concentrated solui ion is mixed with 

 a large excess of a concentrated solution of caustic potash in 

 methyl alcohol, and the mixture cooled by ice, a potassium salt 

 of the composition NOj . NK . COOK is deposited in crystal 

 plates. If these crystals are placed in water they instanl'.y de- 

 compose with great rise of temperature into potassium carbonate 

 and nitrous oxide. If, however, they are placed in a mixture 

 of ice and sulphuric acid, carbon dioxide is evolved, and the new- 

 substance nitramide is produced. It may be extracted by 

 means of ether, and upon evaporation of the latter it is left 

 behind in the form of clear colourless prisms. The crystals 

 melt at 72', but the least trace of moisture lowers the melting 

 point very considerably. Nitramide is readily soluble in water, 

 ether, and alcohol, but dilificulily solulile in benzene. The 

 aqueous solution reacts strongly acid. Nitramide is volatile, 

 <;onsidtrably so even at the ordinary temperature. It is an un- 

 stable substance, and decomposes on mixing with copper oxide 

 or lead chromale, or even on admixture with powdered glass, 

 great rise of temperature occurring in each case. The products 

 of decomposition are nitrous oxide and water. When heated 

 rapidly above its melting point it explodes. Nitramide is 

 instantly decomposed by alkalies, not only by caustic alkalies but 

 also by carbonates, ammonia, borax, and even sodium acetate, 

 in the cold, with evolution of nitrous oxide. It would thus 

 appear to be incapable of forming salts, at any rate in solution. 

 The crystals explode violently, with production of flame, when 

 a drop of caustic soda or potash is allowed to fall upon them. 

 The ethereal solution of the crystals yields with ammonia a 

 precipitate of an ammonium salt, but it decomposes almost 

 immediately with evolution of gas. Concentrated sulphuric 

 acid or hot water similaily provoke violent decomposition. 

 Upon reduction a substance endowed with powerful reducing 

 NO. 1292, VOL. 50] 



properties is produced, which would appear to be hydrazine 

 NH„ 



I '. The discoverers of this interesting substance are con- 

 NH„ 



tinuing the study of its reactions, and are attempting to prepare 

 it in a purely inorganic manner. 



The additions to the Zoological Society's Gardens during the 

 past week include a Vervet Monkey (Cercopithtcus hilandii), a 

 Hygian Snake (Elaps liygis) from South Africa, presented by 

 Mr. J. E. Matcham ; a Macaque ^lonVty {Macacus cynomolgus) 

 from India, presented by Mr. J. A. Brand ; a Common Para- 

 doxure (Paracloxurus typus) from India, presented by Mr. E. 

 Stallard ; a Suricate (Siiricala tetradactyla] from South Africa, 

 presented by Miss Champneys ; an Indian Cobra [Naia tripu- 

 dians) from' India, presented by Mr. Angus M. Kinloch ; two 

 Slowworms [Angtiis fragilis), British, presented by Mr. T. E. 



Gunn ; two Opossums (Didilphys, si>. \nc.) horn South 



America, a Common Cassowary (Casuarius galealus) from 

 Ceram, a Hawk-headed Parrot (Deroptyus accipitrinus) from 

 Brazil, two Hamadryads (Op/'iiophagus claps) from India, de- 

 posited ; a Pleasant Antelope (Tragelap/iiis grains), bred in 

 Germany, purchased ; a Thar (Capra jemlaica), a Red Deer 

 {Cervus elaphus), three Cairo Spiny Mice (^fffwyf cahirinus), 

 bom in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



Spectroscopic Velocities of Bi.naries. — The determina- 

 tion of the elements of double-star orliits from spectroscopic 

 measurements has been attempted by two methods. That due 

 to Dr. Wilsing, which is a very convenient one, is only appli- 

 cable to cases of small eccentricities ; another method, developed 

 by Dr. Rambaut, is not subject to this limitation, but is rather 

 elaborate. In No. 3242 of the Astronomische Nachrichlen, 

 Prof. R. Lehmann-Filhes works out a mctho 1 somewhat akin to 

 that of Dr. Rambaut, but which he claims to have discovered 

 independently, and which does not require difficult calculations 

 or constructions. If both components of a spectroscopic double 

 are bright enough to give a measurable spectrum, as is the case 

 with & Aurigx and C Ur-x Majoris, the velocities as de- 

 termined from the displacement of the lines in the spec- 

 trum are taken as relative, and the investigation then deals 

 with the motion of one mass with respect to the other 

 considered as stationary. If, on the contrary, only one of 

 the components gives a measurable spectrum, as in the case of 

 Algol and a. Virginia, the motion must be referred to the centre 

 of gravity of the system, the radial velocity of which must be 

 determined and subtracted from the observed velocities. The 

 period of the star is easily determined by observing a consider- 

 able number of periodic variations, and all observations can 

 then be reduced to a single revolution by adding or subtracting 

 multiples of the period. These spectroscopic velocities are then 

 plotted as ordinates with the times as al scissce, and a wavy 

 curve is thus obtained showing the maximuui and minimum 

 velocities relative to the solar sysiem. If these velocities are 

 referred to the centre of gravity ot the sy>tem, the areas of the 

 curve above the axis ot abscissa; must be equal to those below, 

 i.e. the total displacemenis must neutralise each other. This 

 gives a condition which the curve must lulfil, and which serves 

 to control the observed velocities. Another condition is that 

 the area inteicepted between the maximum positive ordinate 

 and the next point of intersection with the axis of abcissK must 

 be equal to the area of the curve between that point and the 

 maximum negative ordinate, this representing the motion of 

 the star from the ascending to the descending node. Prof. 

 Lehmann-Filhcs gives simple formulce lor determining the 

 various elements of the orbit from the cotrccied curve. Com- 

 paring hi.s mtthod with that of Dr. Rambaut lor the case of 

 R Auriga?, he finds o'isS for ihe tccenlricity, where the 

 latter lound o 156, and 57 '93 lor the longitude of ihe 

 ascending node, against Dr. Rambaut's 5/"43, showing diflci- 

 enets which are well within the errors of oijscrvation. The 

 real daily motion is (ourd to be 90''726, coiiesponding to a 

 period ol 3'968days. The apparent semi-major axis of the oibit 

 comes out as 7,516,000 English miles, which agrees very closely 

 with the value obtained by Dr. Rambaut, viz. 7,500,000. 



