Oct. 28, 1880] 



NATURE 



617 



the opinion expressed by Dr. Julius Schmidt from his earlier 

 observations, the true period of this notable variable star, instead 

 of being a little less than five days, appears to be a little less 

 than half this interval, otherwise mininm observed at Harvard 

 College, will not accord with those of May and August observed 

 in Europe. 



It is probable that Schwerd observed the star near a maximum 

 at meridian transit at Speyer on March II, 182S, when he 

 estimated its magnitude 67, and near a minimum at transit on 

 May 12 in the same year, when he rated it only lom. If we 

 compare the observation of March 1 1 with that of Dr. Schmidt, 

 who fixed a minimum to August 12 at 6h. mean time at Athens, 

 and assume 7662 periods to be included in the interval, we get 

 for the duration of one period 2'49oS4d., or 2d. llh. 46'SirQ., 

 which closely accords with half the period assigned by Schmidt 

 from his own observations and those of Ceraski. This reckoning 

 from August l2'lS4l Greenwich mean time, and correcting for 

 the light-equation, will give the following times of geocentric 

 minima observable in this country : — 



Oct. 28 



Nov. 2 

 7 



Nov. 17 



27 



7 47 G.M.T. 

 7 21 „ 

 6 54 » 

 6 28 



9 33 G.M.T 



9 7.. 1 



S 40 „ 



8 14 „ I Dec, 

 And for the times of visible maxima, supposing this phase to 

 occur midway between the minima, we find — 



h. m. I h. m. 



G.M.T. Nov. 



[ Dec. 



If S be the sun's longitude, and R the earth's radius-vector, 

 the correction for the light-equation (geocentric — heliocentric) 

 for iSSo may be found from 



Cor. = 224*os R. sin (S -F 19° I7''4). 



We have received from Lord Lindsay a circular containing 

 the same information that is given in Prof. Pickering's letter, 

 with the addition of a diagram showing the Durchmustcruitg 

 stars in the vicinity of the variable, which for iSSl'O has R.A. 

 oh. Sim. 48s., N.P.D. 8° Ad'o. 



[Mr. Knott's obsei-vation on October 23, received' since the 

 above was in type, as compared with Athens August 12, seems 

 to require a somewhat longer period, with minima a half hour or 

 so later than we have computed.] 



The Rotation of Jupiter. — In No. 2,342 of the Astrono- 

 mische Nachrichten (to which we refer for numerical details) Dr. 

 Julius Schmidt has a communication wherein he finds, from 

 obsep.-ations of the red spot upon the disk of Jupiter by himself 

 and others in 1S79-S0, an interval of gh. SSm. 34'4s. for the 

 time of the planet's rotation upon its axis, a result that he con- 

 siders may be adopted until the observations generally have 

 attained a greater degree of precision than they appear to 

 possess at present. With due care and practice, however, he 

 believes that such observations will be found to admit of much 

 gi-eater accuracy, and illustrates this by his own experience at 

 Athens ia the present year. In the same communication he 

 also discusses observations of a dark ov.il spot (a more favour- 

 able object than any used by Airy and Madler) during 104 rota- 

 tions in 1S62 ; these observations give gh. SSm. 25'6Ss. for the 

 period of rotation, a result closely agreeing with those of 

 1834-35- 



CHEMICAL NOTES 



A NEW method of preparing acetylene is described by Dr. W. 

 Suida in Wicu. Akad. Bcr. The method consists in heating 

 iodoform and mercury ethide in sealed tubes to 120° ; the pro- 

 ducts of the reaction are acetylene, ethylene, ethylic iodide, and 

 mercury ethyliodide. 



The same Berichte contains a paper by Herr v. Dumreicher 

 on the relative stabilities of nitrous and nitric oxides, and of 

 nitrous and nitric oxides when acted on stannous chloride. 

 Nitrous oxide is not reduced even at 100° ; nitrous acid is re- 

 duced to nitrous oxide ; nitric oxide and nitric acid ■ are reduced 

 to hydroxylamine, and subsequently to ammonia. The reaction 

 may be applied to the estimation of nitric acid. 



In the Proceedings of the Academy of Rome Signor Cossa 

 communicates the results of experiments on didymium tungstate : 

 he has determined the specific heat of this salt to be 0'o83i — 



temperaturature limits are not given. Taking the atomic heat of 

 tungsten as 6-4, and that of oxgen as 4, this result points rather 

 to the formula for didymium tungstate, DiW04(Di = 98), than 

 to that now generally accepted, Di„(W04)3(Di = 147). _ 



A NEW organo-nietallic compound containing the divalent 

 radicle (CH.,)" is described in the Journal of the Chemical 

 Society by Sakurai ; the formula of the new substance, for 

 which the name Monomercuric methylene iodide is proposed is 

 I(CH2)HgI. This is the first known metallic, compound con- 

 taining a divalent hydrocarbon radicle. 



G. BoucHARD.\T claims, in Compt. rend., to have converted 

 amylene, by successive removals of hydrogen, into cymene. 

 Hitherto attempts to pass, by a simple series of reactions, similar 

 to those by wliich the passage from one isologous group to 

 another is effected, from the paraffin to the aromatic group of 

 compounds, have not been successful. 



According to the experiments of Macagno (Bi:d. Cenlralbalf) 

 the mellowness of old wine is due more to an increase in the 

 amount of glycerine present, than to a decrease in the tannin ; 

 there must also be a certain proportion between the amounts of 

 alcohol and tannin, in order that the wine may keep w^ell. 



In the Annates Chim. rhys. Berthelot describes an apparatus 

 in which the combination of two gaseous constituents to form a 

 gaseous compound may be conducted, so as to allow of an 

 accurate measurement of the thermal change which accompanies 

 the chemical change. 



A DISCUSSION as to the value to be assigned to the atomic 

 weight of antimony is at present being carried on. From 

 anafyses of the bromide and other salts. Prof. Cooke of Harvard 

 concludes that the generally-accepted number, 122, is too large, 

 and that 120 is more nearly correct. Herr Schneider, whose 

 experiments had been criticised by Cooke, replies in the Journal 

 fiir Pract. C/icm. He sharply criticises Cooke's methods, gives 

 the details of neu- experiments, and asserts strongly that 122 is 

 much more nearly correct than 120. 



No results of special importance have lately been published 

 regarding the densities of the vapours of the halogen elements. 

 An objection made by Pettersson and Ekstrand to V. Meyer s 

 method, viz. that solid bodies condense air on then- surface, 

 which air they again give up when strongly heated, has been 

 shown by Meyer, in the last number of the Berlin Bcnchte, to 

 have no weight against his experiments. 



Two important papers on atmospheric ozone have been pub- 

 lished in the Berichte by E. Schbne. This observer, who has 

 given much careful study to the subject of ozone, says that 

 the smell of ozonised oxygen does not at all resemble the peculiar 

 odour noticed after a lightning flash. The true smell of ozone 

 is, however, frequently noticeable in ordinary air, and coming from 

 the clothes of persons who may enter a room from the open air in 

 winter. The ordinary potassium iodine papers are valueles-, as 

 ozone measurers, according to Schoue. A small amount of ozone 

 in moi-t air produces a greater depth of colour on these papers than 

 a lamer amount of ozone in dry air. The humidity of the air and 

 the hyf^roscopic character of the material from which the paper 

 is made therefore largely influence the depth of colour produced. 

 It has been supposed that much ozone is produced in the neigh- 

 bourhood of waterfalls, but the increased depth of colour of the 

 potassium iodide papers is only due, says Schone, to the great 

 humidity of the air. Schbnbein's "ozonometer" serves as a 

 very rough hygrometer. Paper coated with thallous hydrate is 

 recommeiided as a measurer of the relative amount of " oxidising 

 principle" in the air: the paper is coloured brown— owing to 

 production of thallic oxide— by ozone or hydrogen peroxide. A 

 table is given showing the variations in "oxidising principle 

 durin» 1S79. The general conclusions are briefly these:—!. 

 The papers are coloured more deeply during the day than during 

 the ni"ht ; this difterence is more apparent during the long days 

 of the year. 2. Increased wind-force causes increased colora- 

 tion, because a greater amount of oxidising substance is brought 

 in contact with the paper during the time of exposure. 3. 

 Cloudiness and rain especially influence the coloration ; the 

 heavier the rain the smaller the coloration of the paper. iJ'rect 

 determinations of hydrogen peroxide have shown that when the 

 thallium papers are much coloured this compound is present m 

 the atmosphere in comparauvely large qumtity. Herr Schone 

 regards the actual existence of ozone in the atmosphere as at 

 present an open question. 



Mr a. Villiers publishes in the September number of 

 Annales Chim. Phys. a lengthy and important paper on the 



