i3» 



NATURE 



\Junc%, 1882 



J. W. Bruhl, from the results of determinations of molecular 

 refractions of many carbon compounds, concluded that the 

 atomic refraction of carbon varies according as the atoms of 

 carbon are tetravalent, divalent, or monovalent (singly, doubly, 

 or trebly "linked"), in the molecule under consideration. In 

 calculating molecular refractions, Briihl used the empirical 



expression '^—^ — "M ; Landolt has recently re-calculated the 



d 

 ratios ot many molecular refractions by the use of the formula 



— "M, deduced by Lorenz from the theory of light ; his 



(«'-' + 2)d 



results entirely confirm those arrived at by Briihl by the use of 



the empirical expression stated above 



In their researches on ozone, MM. Chappuis and Hautefeuille 

 have made use of the spectroscope to trace the progress of the 

 chemical change which occurs when oxygen, or a mixture of 

 oxygen and nitrogen, is subjected to the action of the electric 

 discharge. They find that ozone is characterised by a distinct 

 absirptive spectrum, the prominent bands in which are two in 

 number situated in the neighbourhood of D. The same bands 

 are prominent in the absorptive spectrum of liquid ozone. 



MM. Chappuis and Hautefeuille also find that the 

 amount ot ozone produced by the action of the electric dis- 

 charge on a mixture of oxygen and nitrogen increases to a 

 maximum, then decreases to a minimum, then again increase-, 

 and so on ; by the aid of the spectroscopic method they trace 

 this oscillation to the formation and decomposition of an oxide 

 of nitrogen not hitherto observed, which they propo-e to call 

 pernitric oxide {acide pernitrique) {Comfit, rend., xci v, 858 and 

 mi). 



The Journal of the Society of Chemical Industry, the fourth 

 number of which is now before us, promises to be of very great 

 service to all who are interested in chemical manufactures. The 

 present number of the journal contains papers read before the 

 Society on " Smoke Abatement," "The Chemical Technology 

 of Jute Fibre," " The loss of Sulphuric Acid in the Manufacture 

 of Salt Cake," &c. Note-; on the more important recent 

 technical applications of chemistry and chemical physics, and 

 very useful classified abstracts of recent patents complete the 

 number. 



In the last number of the Berkhte of the German Chemical 

 Society (xv. 1161) HH. v. Meyer and H. Goldschmidt describe 

 an apparatus by means of which the specific gravities of gases 

 may be determined at very high temperatures. The apparatus 

 concists of a cylindrical porcelain tube 500 or 600 mm. in length, 

 capacity about 100 c.c, furnished with a capillary tube of about 

 20OC.C. long at each end. The apparatus is heated, the air is 

 driven out by an inert gas, e.g. by nitrogen, the gas whose 

 specific gravity is required is allowed to enter the appa-atus, and 

 the weight of this gas is determined by driving it out, by means 

 of an inert gas, into some liquid by which it is completely ab- 

 sorbed. The temperature may be calculated from the ratio 

 between the volume of air contained in the apparatus under the 

 conditions of the experiment and the volume contained at the 

 ordinary temperature of the room. By the use of this apparatus 

 the authors have determined that the density of cyanogen is 

 normal {i.e. corresponds with the formula C S N S ) between 100° 

 and 800°, but that at 1200° this gas is decomposed with evolution 

 of nitrogen. 



PHYSICAL NOTES 

 A NEW method of comparing the brightness of different 

 coloured lights has been proposed by Heir Briicke ( H'ieu. Be?-., 

 84). He finds that objects cease to be visible at a greater visual 

 angle, the more they differ from the background on which they 

 are seen, only in colour and not in brightness. If a board be 

 set up, which is black at one end and white at the other, with 

 successive shades of grey between (a brightness-table), one may 

 determine the brightness, e.g. of a coloured paper, by placing a 

 piece of it before different parts of the board, and noting the 

 place where, with shortest interval, it becomes invisible. This 

 relation of brightness, in red and blue, varies much with the 

 strength of illumination, so that each determination becomes in- 

 valid, where the illumination is considerably altered. Herr 

 Briicke believes such a table might be useful in the colourless 

 reproduction of paintings (drawings, copper-plate engravings, 

 &c). Further, he constructs a photometer, in which, instead of 



the brightness-table, he employs a variable illumination of the 

 object to be distinguished from it. 



The specific gravity of liquid steel has been determined by 

 Herr Alexjeff, by a method proposed by Herr Petruschewsky 

 (J. d. Suss. Chem. Phys. Ber. ,12). A porcelain tube, open at 

 both ends, was connected at one end with a forcing pump and a 

 manometer, while the other end was immersed in liquid steel to a 

 given depth (the tube vertical). On pumping, bubbles appeared 

 at the latter end ; and the indication of the manometer at that 

 moment, compared with the depth of immersion, served for de- 

 termination of the relative density of the steel and the liquid 

 (naphtha) used in the manometer. The specific gravity of 

 liquid steel was thus found to be 8 '05, and so, greater than that 

 of solid steel. 



According to Herr Antolik {Wied. Attn., 3) very regular 

 and pure Lichtenberg figures are obtained on spherical glass 

 vessels filled with warm water at about 60° C. The surface can 

 be made at will electrically positive or negative (which is not the 

 case with ebonite or resin). Wires are inserted which are fur- 

 nished with balls at their upper end. If positive electricity be 

 introduced, electricity of that kind becomes free at the surface, 

 and on dusting with Villarsy's mixture, a quite homogeneous 

 sulphur layer is produced. Very regular discs appear on drawing 

 sparks with the knuckles. A number of interesting effects are 

 described by the author. 



Prof. H. M. Taul has communicated to the Seismological 

 Society of Japan some notes on the effect of railway trains in 

 transmitting vibrations through the ground. A box holding 

 about twenty pounds of mercury thickened by amalgamation 

 with tin, was placed upon a heavy plank screwed to the top of 

 a post sunk 4^ feet into the ground. Images reflected in the 

 surface of the mercury were observed by a telescope, as in 

 meridian ob-ervations. An express train passing at a distance 

 of one-third of a mile, set the surface of the mercury in con- 

 fused vibration for two or three minutes. Other observations 

 were made at stations at somewhat greater distances. The ex- 

 perimenter also found that a one-horse vehicle passing along a 

 gravelled road 400 or 500 feet distant, caused a temporary 

 agitation of the mercury whenever the wheels struck a small 

 stone. 



An extremely valuable series of notes on physiological optics, 

 from the pen of \V. Le Conte Stevens, has lately appeared in 

 the American Journal of .Science: most of these relate to stereo- 

 scopic vision and the theory of the stereoscope. They are both 

 too valuable and too full of matter to render full justice possible 

 in a brief note. 



A NEW form of refractometer, producing interference-bands 

 and rings between tuo pencils of light which have traversed 

 paths at right angles to each other, is described by Mr. A. A. 

 Michelson in the American Journal of Science. In the path ot 

 a ray from a lamp, a piece of plane-parallel glass is interposed 

 at 45°. The two pencils respectively reflected and refracted are 

 then returned along their own paths by mirrors normal to each ; 

 and these returning rays unite at the point whence they parted, 

 giving a resultant ray at right angles to the former path. The 

 theory of this refractometer is deduced by Mr. Michelson, who 

 devised this apparatus for u-e in his experiments to test the 

 hypothesis of a relative velocity between the earth and the 

 luminiferous aether. 



M. Violle finds the temperature of fusion of zinc free from 

 lead, cadmium, arsenic, and other impurities to be 929*6° (C); 

 the value previously found by Edm. Becquerel was 932° ; that 

 given by Sainte-Claire Deville and Troost being 1040°. 



The rapidly-reversed currents generated in an ordinary Bell 

 telephone do not sensibly affect the needle of a galvanometer 

 even when the loudest tones are being sung into the instrument. 

 Nevertheless M. Chardonnet has made the curious and interest- 

 ing observation that during the short period while the note is 

 increasing or diminishing in intensity, a deviation of the needle 

 is observed. The explanation advanced is that during the rise 

 or fall in intensity the alternate currents are no longer of *_qual 

 strength, the odd semi-oscillations being either greater or less in 

 amplitude than the even semi-oscillations during the period of 

 rise or fall. 



Some interesting new pieces of acoustical apparatus have been 

 recently described by Herr Hartmann {IVied. Beibl. No. 3). 

 The motorophone shows the change of rotatory motion into 



