114 



NA TURE 



[November 29, 1894 



other half has twelve arcs of concentric circles drawn upon it. 

 Each arc subtends an angle of forty-five degrees. In the first 

 quadrant there are three such concentric arcs, in the next three 

 more, and so on ; the only difference being that the arcs are 

 parts of circles of which the radii increase in arithmetical pro- 

 gression. Each quadrant thus contains a group of arcs differ- 

 ing in length from those of the other quadrants. The curious 

 point is that when this disc is revolved, the impression of con- 

 centric circles of different colours is produced upon the retina. 

 If the direction of rotation is reversed, the order of these tints 

 is also reversed. The cause of these appearances does not 

 appear to have been exactly worked out. 



The additions to the Zoological Society's Gardens during the 

 past week include a Black Lemur {Lemur macaco, { ) from 

 Madagascar, presented by Mr. Roche ; a Snowy Owl (A'yctea 

 scanditua), captured in mid-.\tlantic, 700 miles from land, 

 presented by Mr. Harston Eagle : two Levaillant's Cynictis 

 (Cynictis Itvaillanti), two Domestic Sheep (Ovis aria, var.), 

 two Puff' Adders ( Vipera arietans), a Cape Bucephalus 

 (Bucephalus capeusis), six Hispid Lizards {Agama hispida), five 

 Rough-scaled Lizards [Zonurus corydlus), a Delalande's Lizard 

 (Nucras delalandi), a Crossed Snake (Psammopltis crucifer) from 

 South Africa, two Bennett's Tree Kangaroos {Dendrolagus 

 itnne/iauus) from North Queensland ; an Allied Goshawk 

 (Astur afprcximans), three Long-necked Chelodines {Chelo- 

 dina lon^icollis), twenty-two Golden Tree Frogs (//j/a aurea), 

 seventeen While's Tree Frogs (Hyla dcrula) from Australia, 

 a Spix's Macaw (Ara spixi) from North Brazil, deposited ; two 

 Caroline Conures [Couurus carolinensis) from North America, 

 purchased; two Queensland Tree Kangaroos (Dendrolagtis 

 lumholtzi, i 9 ) from Queensland ; four Brush Turkeys 

 (Tategatla lalhami, 4 <J ) from Australia, received in exchange. 



OUR ASTRONOMICAL COLUMN. 



Tub Parallax of Neiiula k 2241. — .A.t the time when 

 Dr. Wilsing took photographs of the nebula B.D. -|- 4i°-4004 

 for the determination of parallax, he obtained also a series of 

 negatives of B.D. -i- 41 '•4773 (.4 2241) for the sane purpose. 

 This nebula is almost ring-shaped, and displays a cen.ral con- 

 densation. The latter appears more distinct on the photo- 

 graphic plates than can be seen by eye observations, and ils 

 contour is only sufficiently sharp for micromelric measurements 

 on the best plate-, so that the centre of the whole apparent disc 

 has been generally used. From June 1S92 to August of the 

 following year, 33 plates were obtained, 31 of which have been 

 used in this research. .Six comparison stars, the positions of 

 which were taken from the Bonn zones, have been adopted. 

 In ihi- account of the result obtained (Aslro. Nach. No. 3261), 

 Dr. Wilsing gives a table showing the deduced distances of the 

 nebula from the two comparison stars 3 and 6. A second table 

 contains ihe mean monthly values of these distances with their 

 differences from the whole mtan value obtained from all the 

 measuremeni^, toj;cihcr with the most probable errors of the 

 measurements. 



The following table shows these differences between the toial 

 and monthly means for the two stars 3 and 6 : 



IN.3I 



1892 June 21 ... -003 

 July 13 ... -^o■|I 

 Aug. 9 ... +007 

 Sept. 25 ... -HO-OI 

 Oct. 4 ... -0'I3 

 Nov. 8 ... -(-0'20 

 Dec. 22 ... -o 53 



1893 Feb. 4 ... -0-I3 

 July ... -O'oJJ 

 Aug. ... -053 



tN-,61 



Frob. enor. 



•fo-28 ... ±0oS ... S 



-l-o*o3 ... o'o6 ... 9 



-0'04 ... 0-13 ... 2 



-006 ... COS ... 5 



-l-o'oi ... 0-13 ... 2 



+ 003 ... O'lO ... 3 



-044 oiS ... I 



-034 ... 018 ... I 



-019 ... o'i3 ... 2 



-0-14 ... Q-iS ... I 



suggests, to be cautiously dealt with, and he is led to conclude 

 from this series of measures that the relative parallax of this 

 nebula does not exceed one or two tenths of a second of arc. 



.•V Possible New Zo.ne of Asteroids. — The secular 

 variations of the orbits of the four inner planets has lately 

 occupied Prof. Newcomb's attention, with the result that 

 several elements h-ive been found to vary in a manner un- 

 accounted for by existing theory. {Astronomical J ouriia!. No. 

 327.) "These anomalies," says Prof. Newcomb, "cannot be 

 simultaneously explained either by an intra-mercurial zone of 

 planets, by the action of matter rellecting the zodiacal light, or 

 by a deviation of gravitation from the usually accepted law. 

 The uncertainty as to the mass of Mercury makes the construc- 

 tion even of a working hypothesis difficult ; but apart from all 

 considerations of probabilities, .! priori, the hypothesis which 

 best represents observations, is that of a ring of planetoids of 

 small eccentricity a little outside the orbit of Mercury, and a 

 little more inclined to the ecliptic. The total m.iss of the ring 

 may range from one-fiftieth to, perhaps, one three-hundredth of 

 the mass of Venus, according to its distance from Mercury." 

 Prof. Newcomb intends to carefully investigate the matter in 

 order "to decide whether the results of the hypothesis are such 

 as to counterbalance its extreme improbability." 



A New Co.met. — Edinburgh Circular, No. 43, dated 

 November 23, stales that a telegram received from the Central 

 Astronomical Station at Kiel announces the discovery of a very 

 faint comet, by Mr. Edward Swift, at 8 p.m., Californian time, 

 on the 20th inst. It was situated in Right .\scension, 22h. iSm. 

 24s., and South Declination, 13° 7', and was moving slowly 

 towards the east. 



No. ..r 



plates. 



The«e differences, wh;n considered in relation with the 

 probable errori of the measurements, have as Dr. Wilsing 



NO. 1309. VOL. 5 l] 



A NEW SERIES OF NITROGEN COMPOUNDS. 



A NOTHER new series of nitrogen compounds, containing 

 •**• four atoms of that element along with one atom of carboD 

 in a closed chain, are described by Prof. v. Pechmann and Ilerr 

 Runge in the current Bcrichte. They are termed " tetra- 

 zolium " compounds, and the parent base of the series is tetra- 

 zolium hydroxide, whose constitution is represented by the 



^N-NH 

 formula HC; | ,, . The fundamental base itself has 



'\ 



N N 



\, 



II • 

 OH 



not yet been isola'ed ; the compounds prepared comprise the 

 derivative in which the two hydrogen atoms directly attached 

 to the two end nitrogen atoms are replaced by phenyl, together 

 with a large number of salts of this base, formed by replace- 

 ment of the hydroxy! by halogens or other acid radicles just as 

 in the case of metallic hydroxides. The hydrogen atom atl.\checl 

 to the carbon is likewise capable of replacement by many 

 organic radicles, so that a large number of still more compli- 

 cated bases havelikewisebeen prepared, together wilhtheir corre- 

 sponding salts. The hydroxides of this new series are character- 

 ised by possessing strong basic properties. They m.ay all be pre- 

 pared most conveniently from their chlorides, by the action upoi» 

 them of silver oxide. They are extremely soluble in water, but 

 are completely piccipilated from their solutions by ether. The 

 aqueous solutions absorb carbon dioxide ami behave very much 

 like caustic alkalies. They cannot, however, be crystallised, 

 forming rtslns upon concentration. The salts, on the other 

 hand, crystallise admirably ; they are usually soluble in water, 

 react neuiral to litmus, and possess a very bitter taste. Diphenyl 

 ,,N— NPh 



tetrazolium chloride, HCy 



: taken as 



•v I y-Di,. which may be I 



^N -aC 



CI 

 a typical salt of the .series, crystallises in colourless radiating 

 groups of needles very sensitive to light, which renders then> 

 yellow. The aqueous solution yields a ffesh. coloured precipi- 

 tate of a chloroplatinate with platinum chloride, and the double 

 salt may be crystallised from hot water. .V crystalline double 

 chloride is likewise produced with gold chloride. The addition 

 of a soluble nitrate or iodide causes the precipitation of the 

 difficultly soluble nitrate or iodide of the base. A solution of 

 iodine in potassium iodide precipitates an iodine addition pro- 

 duct, which can be crystallised from alcohol in beautiful brown 

 tabular crystals exhibiting a violet reflection. The parent base 

 is produced in solution upon the addition of silver oxide, silver 



