Feb. 17, 1881] 



NATURE 



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One of M. Mercadier's recent experiments iu radiophony 

 deser\'es a note. A disU of thin co|-iper about 4 centime, in 

 diameter, heated at its back liy an oxyhydrogen blowpipe, was 

 placed behind a rotating; wheel with apertures, and the inter- 

 mittent heat-rays were received upon one of his sensitive disks 

 of thin metal blackened at the surface. With a brisjht red heat 

 the customary note was well heard from the intermittent beams. 

 On putting out the flame the sound gradually fell off in intensity, 

 but was still audible after the cipper disk had ceased to emit 

 visible rays. All that this experiment ])roves, however, is that 

 the dark rays, when they fall intermittently upon an absorbent 

 surface, can cause it to undergo rapid expansions and contrac- 

 tions ; while Graham Bell's earlier experiment showed that 

 visible rays could produce this result. 



M. CoRNt; discusses in the Comptes rendtis the propositions of 

 M. Gouy concerning the velocity of proi).igalion of light jiro- 

 ceeding from a source of variable amplitude, on which we lately 

 published a note. He denies the truth of M. Gouy's funda- 

 mental assumptions, and concludes thai since all our appliances 

 can only change the amplitude of the waves by ([uantities which 

 may be regarded as constant during a great many successive 

 waves, the formula of waves of persistent type will still hold 

 good, and the velocity of propagation of the amplitudes will be 

 identical with that of the w.aves themselves. 



M. Chappuis thinks th.at the blue of the sky may be due to 

 ozone present in the upper regions of the air. He argues that 

 the electrical discharges constantly taking place will ]iroduce 

 ozone ; and the recent researches of himself and M. Hautefeuille 

 have shown that ozone, at any rate when near its condensation 

 point, is of a blue tint. He has e.xamined theabsor|>tion-spectrum 

 of ozone and find-, nine dark bands in it, three at least of wliich 

 correspond with known bands in the telluric spectrum. 



To obtain enlarged impressions from the phonograph, MM. 

 Roig and Torres (Cronica cUntifica, No. 4) substitute for the 

 metallic membrane which bears the indenting style a plate of 

 mica, quite free at the border, and supported at the centre by 

 an axis of caoutchouc fixed to a small spring. This axis carries, 

 besides the short style for acting on the tin sheet, a small metallic 

 piece in a plane perpendicular to the axis of the style, and this 

 supports a second style, long and thin, the vibrations of which 

 are inscribed on a cylinder blackened with smoke. The same 

 angular velocity is imparted (by means of clockwork) to the 

 cylinder of the phonograph and the blackened cylinder, and 

 while the short style makes its usual marks on the tin, tlie long 

 one produces a larger tracing on the cylinder, which the authors 

 have tried to decipher. They have succeeded easily in recog- 

 nising the different vowels, some consonants, and even some 

 syllables, but they have not been able to read entire phrases. 

 The curves are more characteristic if the voice be used with 

 ordinary intensity ; on forcing it they are deteriorated. 



Prof. Avenarius, of Kiew, has taken out an Austrian 

 patent for a new method of division of the electric light. The 

 method is that of insertion of a polariser in a secondary circuit, 

 coimected with each electric lamp. The polariser, consists of 

 several voltameters connected together. The current, supplied 

 by an electrodynamic machine, divides before entering each 

 lamp : one part goes through the la'up, while the second goes 

 through the secondary circuit and the polariser and then back 

 to the primary circuit. l!y insertion of a considerable resistance, 

 eg. increase of the voltameters, the light-inlen-ity of the lamps 

 may be varied. The individual lamps are independent of each 

 other, and lam])s of different systems may be simultaneoudy 

 used. 



We notice in the minutes of meetings of the Russian Physical 

 and Chemical Society (vol. xii. fasc. 9) the reseaiches, by M, 

 Glasenap, on refraction. The want of concentricity of sheets 

 of air of equal density produces a certain variation in the nor- 

 mal refraction given in the tables ; the surfaces of equal density 

 being as a rule inclined to .some degree instead of being hori- 

 zontal, and the degree of inclination being submitted to a certain 

 periodicity during a whole year, there necessarily arises from 

 this cause a certain correcti jn to be applied to the observed 

 position of a star, much hke to that of the annual parallax and 

 aberration, and which might be described as "parallax of re- 

 fraction." As this correction must obviously affect the values 

 of the annual parallax and of aberration, it is easy to under- 

 stand the necessity to determine its true value with much accu- 

 racy. 1 he values deduced by M. Glasenap for the stars 1 of 



the Ursre Majoris, 1 and O Uraconis, are -o"'04, -o"'il, and 

 — o"'li, which figures would explain to a certain extent the 

 negative parallaxes received by M. Nyrdn ("Nutation der 

 Erdaxe"), and which respectively are -"■03, — o"'05, and 

 -o""i6. The whole work of M. Glasenap on this subject will 

 soon he published. 



CHEMICAL NOTES 



The inflnence of time on processes of chemical change has 

 not yet been thoroughly investigated. In a recent number of 

 Comptes nndus Hcrthelot makes a co)itribution to this sulijcct 

 which is scarcely likely to be accepted by chemists without 

 further investigation. From the results of many thcrmo-chemi- 

 cal measurements Berthelot states that the chemical change, 

 which occurs when an acid soluble in water acts on a s )luble 

 base or salt, or vice versa, or when two soluble salts mutually 

 react, is completed in a space of time mt appreciably greater 

 than that required for completely mixing the two solutions. 



From experiments on the evolution of carbon dioxide from 

 the roots of ]ilants, detailed in the Jiiill. de hi Soc. bolanujue 

 de France, M. Cauvet concludes that carbon dioxide is certainly 

 evolved from plant-roots ; that the (juantity evolved is less during 

 night than during day ; and that the quantity evolved increases 

 at sunrise, decreases towards midday, and again increases in the 

 evening. 



Herr Salleron describes in A'attirforschcr an instance of 

 the modifying influence of moderately heated liquids on glass. 

 An ai^eometcr used in a sugar-work lost about o'5grui. in weight 

 after immeision for eight days in a sugar syrup at 95°. The 

 syrup contained 1 15 grm. sugar and 91 grm. ash per litre. 

 After a few more days the glass split off in splinters. 



Mr. a. a. Nesiut has recently patented a very ingenious 

 process for preventing fraudulent alterations of bankers' cheques. 

 Mr. Nesbit prints his cheques with a dye or dyes, the colour of 

 which is dilVercntly changed by acids and by alUalies ; the inscrip- 

 tions o\\ the cheques are apparent by virtue of the alkalinity 

 or acidity of the dye. Immersion in dilute acid — for the pur- 

 pose of dissolving out the written part of the cheque — causes 

 the whole inscription to bjcome acid tint ; as subsequent treat- 

 ment with alkali changes the whole inscripiion to alkaline tint, 

 the original inscription cannot be restored. If the acid part of 

 the inscription be printed with a dye which is more strongly acid 

 than the alkaline part is alkaline, treatment of the cheque with a 

 neutral solvent of writing ink suffices to blur the inscription, .and 

 this blurring cannot be removed. Various modifications of the 

 invention, and details of the processes of printing, colours used, 

 &c., are given in the specification. 



M. Etard thinks that boron shows certain analogies with 

 vanadium ; in endeavouring further to illustrate such analogies 

 he has obt.iined indications, although not yet positive proof, of 

 the existence of an acid containing more oxygen than boric acid. 

 He has also obtained, by the action of a saturated solution of 

 boric acid on hydrated barium dioxide, a salt to which he gives 

 the formula P.^Oj . liaO . 3H„0, and the name barium perborate. 

 This salt dissolves in acids with evolution of oxygen ; it is 

 very deliquescent (Compt. rend.). 



In continuation of his investigation into the compounds of 

 sulphur and niirogen M. Demarcay describes {Compt. rend.) 

 various bodies which he regards as compounds of the radicle — 

 (S4N3)' — called by him thiolriazyl. The more important of the 

 new compounds are formulated as (S4N.,)CI, (SjN.jjNOj, and 

 (S^NaJH-SOj. 



LlEBEN describes (in Wien. Akad. Jier.) several compounds of 

 calcium chloride with fatty acids, more especially the three 

 compounds with butyric acid, viz. : — 



CaCl., . CjHgO., ; CaCU . 2C4H8O., . 2H.,0 ; and 

 CaCla . Ca(C4H,02)„ . 4C4H8O.J 

 M. Byasson states (Compt. rend.) that if every trace of sul- 

 phurous acid be removed from chloral, the latter retains its 

 liquid condition for an indefinite time, and that the change into 

 solid melachloral, which soon takes place in chloral pnrified 

 only by distillation, may be thus prevented. To remove the 

 last traces of sulphurous acid M. 13yasson agitates the chloral 

 with yjo of its weight of finely-powdered caustic baryta, decants 

 the liquid, and distils. 



