July 9, 1891] 



NATURE 



557 



colour of the product formed on the peroxide plate during 

 discharge, and the reducibility of the sulphate, the author 

 points out that the colour is due to the incomplete reduction 

 of the peroxide ; and that careful examination of the plugs frjm 

 a discharged cell shows that the base consists of practically un- 

 altered peroxide of lead, and that the surface, which is rich in 

 PbS04, is really a mass of partially reduced granules of peroxide 

 of lead which are coated with sulphate. 



Also, though pure lead sulphate is very difficult to reduce, it 

 is well known that mixtures of lead sulphate and peroxide of 

 lead, or other conducting substances, are reduced with com- 

 parative ease, and that it is very intimate mixtures of this nature 

 which have to be dealt with as a rule in charging a cell. 



In conclusion, the author points out — 



That neither chemical nor electrical tests give any ground for 

 apposing that any other sulphate than the ordinary white PbS04 

 ^ concerned in the interactions occurring in the cell ; 



That were the sudden lowering of the E.M.F. caused by a 

 change in the nature of the chemicl compounds formed on the 

 plates, it is very difficult to accouwi. for the very rapid recovery 

 of the E.M.F. exhibited by an apparently discharged cell. 



In the second section the electrolyte is dealt with, and, after 

 referring to the work of Berthelot, Richarz, Schone,Traube, and 

 others on the electrolysis of sulphuric acid solutions, the author 

 describes experiments made to test the effect of the addition of 

 sodium sulphate to the electrolyte, as recommended by Mr. 

 r>arbour Starkey, as it seemed probable it had a catalytic action 

 on the " peroxides " always found in electroiyzed acid of the 

 strength used in batteries. 



Mr. Preece most kindly aided the investigation by allowing 

 experiments to be carried out at the General Post Office, where 

 one-half of the secondary cells contain i per cent, of sodium 

 sulphate, and the other half ordinary dilute acid, sp. gr, i i8o. 

 It was found that the addition of sodiuin sulphate in about the 

 jiroportion of i per cent, to freshly electroiyzed acid, or during 

 electrolysis, always produced a diminution in the total quantity 

 of "active oxygen," and brought the amount present in the plain 

 cells down almost exactly to that found in the sodium sulphate 

 cells. 



Determinations were made of the amounts of "active oxygen " 

 present as persulphuric acid and hydrogen dioxide respectively ; 

 and it was established that acid taken from the cell reduced 

 peroxide of lead. The presence of hydrogen dioxide being thus 

 established both directly and indirectly, its effect on the E.M.F. 

 of a cell was tested. It was found thatj while its addition to 

 the acid in the case of a lead lead-peroxide couple in dilute 

 sulphuric acid produced an annulment, or reversal, of the 

 IIM.F., the introduction of hydrogen dioxide into the body of 

 the peroxide paste produced an increase in the E.M.F. in the 

 case of a platinum lead-peroxide couple. 



The Pust Office records showed that, while the general cha- 

 racter of the temperature and specific gravity changes occurring 

 during charge and discharge were the same in both types of 

 cell, there was less sulphating with the sodium sulphate elec- 

 trolyte. 



The cause of the pink colour of the acid, noticed by Mr. 

 Crompton and others, was investigated, and found to be per- 

 manganic acid, formed probably from the manganese present in 

 commercial lead. 



In conclusion, the author points out — 



That peroxides are found in appreciable quantities in the 

 electrolyte during charge and discharge ; 



That their influence must not be neglected in considering the 

 behaviour of the Plante cell ; 



And that it is to the electrolyte, rather than to the plates, 

 that attention must be directed if any considerable improvement 

 is to be effected. 



" Part II. — A Discussion of the Chemical Changes occurring 

 in the Cell." By H. E. Armstrong, F.R.S., and G. H. 

 Robertson. 



The authors arrive in this paper at the following conclusions : — 



(1) That the cooling observed in the Plante cell can only be 

 explained as resulting from the dissociation of the dilute sul- 

 phuric acid ; and as the values given by Messrs. Ayrton, Lamb, 

 Smith, and Woods are in practical agreement with those calcu- 

 lated on the assumption that the acid used is sulphuric acid 

 itself, H2SO4, that in all probability such acid, and not the 

 dilute acid contained in the cell, is operative throughout. 



(2) That the observed loss in efficiency cannot be due to tem- 



NO. I 132, VOL. 44] 



perature changes, as these arise through actions occurring out o\ 

 circuit. 



(,3) That it is difficult, from a comparison of calculated with 

 ob>erveH values of the E.M.F., to arrive at any final conclusion 

 as to the exact nature of the changes which take place in the 

 cell. On the assumption that sulphating occurs at boih plates 

 in circuit, and under the influence of H2SO4, the calculated 

 value is considerably too high ; while, if sulphating occur only 

 at the lead plate, the value calculated is far too low. 



(4) That a counter E.M.F. of about 0*5 volt would account 

 for the observed departure from the highest calculated value. 

 As peroxides are always present in the electrolyte, it is conciv- 

 able that such a counter E.M.F. may exist ; iiioreover, there is 

 also the possible influence of the lead support to be considered. 



(5) That the observed loss of efficiency is to be attributed 10 

 the formation of peroxidrs in the electrolyte, and to the exces- 

 sive sulphating occurring chiefly at the peroxide plate in the 

 local circuit existing between the support and the paste. 



June 18. — "Comparison of Simultaneous Magnetic Disturb- 

 ances at several Observatories, and Determination of the Value 

 of the Gaussian Coefficients for those Observatories." By I'rof. 

 W. Grylls Adams, D.Sc, F.K.S., Professor of Natural Philo- 

 sophy in King's College, London. 



After drawing attention to previous investigations on this 

 subject, and pointing out the importance of adopting the same 

 scale values for similar instruments at different Observatories, 

 especially at new Observatories which have leen recently 

 established, the discussion of special mngnetic disturbances is 

 undertaken, especially the disturbances of a great magnetic 

 storm which occurred on June 24 and 25, 1885, for which 

 photographic records have been obtained from 17 different 

 Observatories: 1 1 in Europe, i in Canada, i in India, i in 

 China, I in Java, i at Mauritius, and i at Melbourne. 



The records are discussed and compared, tables are formed of 

 the simultaneous disturbances, and the traces are reduced to 

 Greenwich mean time and brought together on the same plates 

 arranged on the same time-scale. Plates I. and II. .>-how the 

 remarkable agreement between the disturbances at the different 

 Observatories, and the tables show that the amount of dis- 

 turbance, especially of horizontal magnetic force, is nearly the 

 same at widely distant stations. 



An attempt has also been made to apply the Gaussian 

 analysis to sudden magnetic disturbances, and, with a view to 

 their application in future work, the values of the Gaussian co- 

 efficients have been obtained for 20 different Observatories, and 

 the numerical equations formed for the elements of magnetic 

 force in three directions mutually at right angles, and also the 

 equation for the magnetic potential in terms of the Gaussian 

 constants to the fourth order. 



The tables give the numerical values to be multiplied by the 

 24 Gaussian constants to give the values of the forces X, Y, and 

 Z in the geographical meridian towards the north, perpendicular 

 to the meridian towards the west, and towards the earth's centre 

 respectively. The equations are also formed and the values 

 obtained in terms of the 24 Gaussian constants for Xg, Vg, and 

 Zj ; Xj being the horizontal force in the magnelic meridian, 

 Yj the horizontal force perpendicular to the magnetic meridian, 

 and Zjthe vertical force. If then Xj, Y^, and Zj be the observed 

 values of any simultaneous disturbances, they may be at once 

 substituted in the equations, the equations giving the 24 

 Gaussian constants may be solved, and the corresponding 

 change of magnetic potential may be determined. 



Physical Society, June 12, 1891. — Prof. W. E. Ayrton, 

 F.R.S., President, in the chair. — Prof. W. G. Adams took 

 the chair whilst Prof. Ayrton read a paper on alternate 

 current and potential difference analogies in the methods of 

 measuring power, by himself and Dr. Sumpner. In a paper 

 read before the Society in March last, the authors pointed out 

 that, for every method of measuring power in which readings of 

 volts and amperes were taken, other methods in which amperes 

 were read instead of volts, and volts instead of amperes, could be 

 devised. More recently, Dr. Fleming had, by a transformation 

 of a formula given by the authors in a communication made to 

 the Royal Society on the measurement of power by three volt- 

 meters, given the analogue in which three ammeters were em- 

 ployed. The two arrangements are represented in Figs. I and 

 2, whilst Fig. 3 shows a modification of Dr. Fleming's method 

 (Fig. 2), in which the current in the non-inductive resistance r is 



