1 86 



NATURE 



[December 24, 



hydroxylamine, NHjOH . HCl, in alcohol, in a flask provided 

 with an inverted condenser, adding the requisite quantity of 

 «inc oxide, and boiling the liquid until it is quite clear. Upon 

 cooling, crystals of the compound are deposited. These crystals 

 are very permanent in their behaviour towards solvents ; they 

 resist organic solvents completely, and are only slightly attacked 

 by water. They are rendered much more unstable by rise of 

 temperature, and explode most violently when an attempt is 

 made to fuse them. If, however, they are carefully warmed up 

 to 120° in a flask connected with a series of U -tubes, they dis- 

 sociate regularly, a gas being rapidly evolved, which condenses 

 to a liquid, mainly in the first U-tube. This liquid is very rich 

 in hydroxylamine, but owing to the dehydrating action of the 

 zinc chloride, contains small quantities of decomposition pro- 

 ducts. This destructive action of the zinc chloride may be 

 altogether avoided, however, if another base capable of replacing 

 the hydroxylamine in the compound is present during the dis- 

 tillation. The base which M. Crismer finds most effective is 

 aniline. About ten grams of the zinc salt are added to twenty 

 cubic centimetres of freshly distilled aniline, and the mixture is 

 submitted to distillation under reduced pressure. Under these 

 circumstances a liquid of very high refractive power distils over. 

 In a few minutes this liquid commences to crystallize in large 

 colourless lamellae, and upon surrounding the receiver with ice- 

 cold water the whole completely crystallizes. These crystals, 

 when washed with a little ether to remove a trace of aniline 

 which is mechanically carried over, are found to correspond to 

 the formula NHgOH. They are identical in all respects with 

 those described by M. Lobry de Bruyn. They dissolve in all 

 proportions in water, and the solution possesses the ordinary 

 properties of aqueous hydroxylamine. The crystals are very 

 deliquescent, attracting moisture with the utmost avidity. They 

 melt at the temperature of the hand. The compound of zinc 

 chloride and aniline, which remains in the distillation flask, may 

 be obtained from solution in boiling alcohol in minute snow- 

 white crystals. 



The second method by which anhydrous hydroxylamine may 

 be prepared consists in passing dry ammonia gas into an emulsion 

 of the zinc compound ZnClg . 2NH2OH in absolute ether. As 

 soon as the first bubbles of ammonia enter the flask an energetic 

 reaction occurs, the zinc salt swells up rapidly, and eventually 

 the whole of the hydroxylamine is liberated, and is dissolved by 

 the ether. The clear ethereal solution is subsequently decanted, 

 and the ether removed by distillation in vacuo, when white 

 crystals of hydroxylamine remain in the vessel in which the dis- 

 tillation is carried out. The only precaution necessary in 

 adopting this mode of preparation is to employ a tolerably large 

 proportion of ether, as hydroxylamine does not dissolve in that 

 liquid to a very large extent. M. Crismer finds it most con- 

 venient to perform the experiment in an apparatus so constructed 

 that the extraction by ether of the product of the action of 

 ammonia is continuous. 



The additions to the Zoological Society's Gardens during the 

 past week include three Rhesus Monkeys {Macacus rhesus S i 9) 

 from India, presented respectively by Dr. Hewetson, Mr. H. 

 Godfrey, and Mr. W. A. Morgan ; a Puma {Felis concolor) 

 from Sante Fe, Argentine Republic, presented by Mr. Thos. 

 Bowers ; a Musanga Paradoxure {Paradoxurus musanga) from 

 the Indian Archipelago, presented by Mr. J. Watson ; a Grey 

 Ichneumon {Herpestes griseus) from India, presented by Mr. 

 W. Needham ; an Azara's Agouti {Dasyprocta azarce) from 

 British Guiana, presented by Mr. R. Scott- Brass ; a Northern 

 Mocking Bird [Mimus polyglottus) from North America, pre- 

 sented by Major N. Gosselin ; two Brown Hysenas {Hyczna 

 brunnea i ?) from South Africa, a Two-toed Sloth {Cholopus 

 didadylus) from Demerara, purchased. 

 NO. I I 56, VOL. 45] 



OUR ASTRONOMICAL COLUMN. 



Capture of Comets by Planets. — During the last two 

 or three years several astronomers have studied the action of 

 planets in changing the orbits of comets which pass near them, 

 and a considerable amount of interest has been aroused in this 

 problem. Prof. H. A. Newton, in the American Journal of 

 Science for September and December, establishes a number of 

 propositions relative to the perturbations by planets which lead 

 to the annexation of comets. Some of the results obtained may 

 be expressed as follows :—(i) If a comet passes in front of 

 Jupiter, the kinetic energy of the comet is diminished ; if it 

 passes behind the planet, the kinetic energy of the comet is in- 

 creased. (2) The greatest effect of perturbation of a planet 

 moving in a circular orbit in shortening the periodic time of a 

 comet originally moving in a parabola is obtained if the comet's 

 original orbit actually intersects the planet's orbit at an angle of 

 45°, and if the comet is due first at the point of intersection, at 

 the instant when the planet's distance therefrom is equal to the 

 planet's distance from the sun multiplied by the ratio of the 

 mass of the planet to the mass of the sun. (3) If in a given 

 period of time 1,000,000,000 comets come in parabolic orbits 

 nearer to the sun thnn Jupiter, 126 of them will have their orbits 

 changed into ellipses with periodic times less than one-half that 

 of Jupiter ; 839 of them will have their orbits changed into 

 ellipses with periodic times less than that of Jupiter ; 1 701 of 

 them will have their orbits changed into ellipses with periodic 

 times less than one and a half times that of Jupiter ; and 2670 

 of them will have their orbits changed into ellipses with periodic 

 times less than twice that of Jupiter. (4) Of the 839 comets 

 which are reduced to have periodic times less than Jupiter's 

 period, 203 will, after perturbation, have retrograde motions, 

 and 639 will have direct motions. (5) Somewhat more than five 

 times as many of these comets move in direct orbits inclined less 

 than 30° to Jupiter's orbit as move in retrograde orbits inclined 

 less than 30° to Jupiter's orbit. It may therefore be said that 

 comets which are changed by the perturbing action of a planet 

 from parabolic orbits of every possible inclination to the ecliptic 

 into short period ellipses must, as a rule, move in orbits of 

 moderate inclination, and with direct motions. 



Law of Limiting Apertures.— The results of some in- 

 teresting photometric experiments connected with the applica- 

 tion of the law of limiting apertures to small object-glasses are 

 given by Dr. E. J. Spitta in Monthly Notices R.A.S., Novem- 

 ber 1891. The apertures of six object-glasses were reduced to 

 one-half and one-quarter respectively, and the intensity of a 

 point at the focus of each was then photometrically tested. The 

 numbers obtained were in neither case proportional to the 

 square of the linear aperture of the object-glass, and they 

 indicated that the outer zones do not contribute as much to the 

 intensity of the image at the focus as they should do theo- 

 retically. Some photometric observations by Dr. Miiller, of 

 Potsdam, also show that the brilliancy of the focal image is only 

 very slightly affected by blotting out the outer parts of his object- 

 glass ; the observed and computed intensities being very dis- 

 cordant until the diameter had been diminished to about one- 

 half. Dr. Spitta believes that the cause of the difference lies in 

 the aplanatisation of the glasses used. 



Connaissance des Temps for 1893, and the extract from 

 the one for 1892, containing information useful for mariners, 

 have just been received from the Bureau des Longitudes. The 

 arrangement appears to be the same as usual, and no comment 

 as to its excellence is needed. 



ORTHOGRAPHY OF GEOGRAPHICAL NAMES. 



'T^HE Council of the Royal Geographical Society have just 

 -^ issued a circular letter, signed by Sir M. E. Grant Duff, 

 the President of the Society, on this important subject. The 

 following are its principal passages : — 



In 1885 the Council, impressed with the necessity of endeavour- 

 ing to reduce the confusion existing in British maps with regard 

 to the spelling of geographical names, in consequence of the 

 variety of systems of orthography used by travellers and others 

 to represent the sound of native place-names in different parts 

 of the world, formally adopted the general principle which had 

 been long used by many, and the recognition of which had been 

 steadily gaining ground, viz. that in writing geographical native 



