Oct. 3, 1889J 



NATURE 



555 



tnentary science, and a comparative decrease in geography. 

 The return of scholars individually examined in the scientific 

 specific subjects shows an actual or relative falling off in every 

 subject except mechanics and chemistry. The rapid and serious 

 decrease of attention paid to these science subjects is shown by 

 the percentage of children who have taken them, as compared 

 with the number of scholars that might have taken these subjects, 

 viz: — In 1882-83, 290 per cent.; in 1883-84, 26 'o per cent.; 

 in 1884-85, 22-6 per cent.; in 1885-86, I9'9 per cent.; in 1886- 

 ^7, l8"i percent.; in 1887-8^, i6'9 per cent.; and it must be 

 remembered that children who have taken two of these subjects 

 count twice over. The Government laid upon the table of the 

 House a new Code, which would have had a slightly beneficial 

 effect upon the teaching of science ; but it has been entirely 

 withdrawn. The Government has introduced no Technical 

 ■Instruction Bill this year— except just at the last moment — and 

 that does not apply to "scholars receiving instruction in an 

 elementary school in the obligatory or standard subjects prescribed 

 by the minutes of the Education Department." It was hurried 

 through the Committee and final stages during the last week of the 

 session. Sir Henry E. Roscoe, however, reintroduced his Bill 

 with some modifications, ana u passed the second reading at a 

 comparatively early period of the session ; but the Government 

 would only give facilities for its progress through the House on 

 the understanding that very serious changes were to be made 

 in it. As he could not accept these, it has not passed the 

 Committee stage ; and it was ultimately withdrawn. Mr. 

 Samuel Smith has again brought in a Continuation Schools 

 Bill ; but there has been no opportunity of discussing it since 

 the first reading, and it was therefore withdrawn. The subject 

 has, however, grown in the estimation of the public ; and the 

 whole question of the teaching of science in State-aided schools 

 requires to be pressed more and more upon the Legislature. 



7\eport of the Committee on Electrical Standards. R. T. 

 Glazebrook, F.R.S., Secretary. (Slightly abridged.) 



The Committee report that the work of testing resistance coils 

 has been continued at the Cavendish Laboratory. A table of 

 the values found for the various coils is given. Further steps 

 have been taken towards the construction of an air condenser. 

 As stated in the last Report, Dr. Alexander Muirhead kindly 

 placed at the disposal of the Committee, for the purpose of ex- 

 periment, three such condensers which he had constructed. A 

 series of tests of these condensers was carried out by the Secre- 

 tary and laid before a meeting of the Committee in London on 

 April 15. It was then decided to adopt Dr. Muirhead's form of 

 condenser for the new instruments of the Comoiittee, and two 

 instruments, each havin:^ a capacity of o"ol microfarad, have 

 'Ijeen ordered from the Cambridge Scientific Instrument Com- 

 pany. They are not yet finished ; a detailed description of their 

 ■design is therefore lefc to the next Report. 



A second subject of investigation has been the specific resist- 

 ance of copper. During the year Mr. T. C. Fitzpatrick has 

 made a large series of experients to determine this, and the Com- 

 mittee desire to thank cordially those manufacturers and others 

 who have given their assistance in this research. Before pub- 

 lishing his results, Mr. Fitzpatrick is desirous of experimenting 

 on some copper which is being prepared for him by chemical 

 means— all which has been used hitherto has been electrically 

 depDsited — and of attempting still further to purify some of the 

 copper already in his possession. Two members of the Com- 

 mittee, Sir VV. Thomson and Mr. Preece, were present at the 

 recent Electrical Congress in Paris. As an English equivalent 

 of the resolutions there passed, the Committee have adopted the 

 following resolutions, which they hope will meet with general 

 acceptance : — 



(i) The name of the practical unit of work shall be the joule. 



The joule is equivalent to lo'' C.G. S, units of work. It is the 

 energy expended during i second by a current of i ampere 

 when traversing a resistance of i ohm. 



(2) The name of the practical unit of power shall be the watt."* 



The watt is the rate of working of a machine performing 

 I joule per second. The power of a machine could naturally be 

 expressed in kilowatts instead of in horse-power. 



{3) The name of the practical unit of light intensity shall be 

 the candle. 



The candle is equal to the twentieth part of the absolute 

 standard of light as defined by the International Conference of 

 1884. 



(4) The name of the practical unit of induction shall be the 

 ^'quadrant." i quadrant is equal to lo^ cm. 



(5) The " period " of an alternating current is the duration of 

 a complete oscillation. ■■■% j 



(6) The " frequency " of an alternating current is the number 

 of complete oscillations per second, 



(7) The " mean current " through a circuit is the time average 

 of the current, and is defined by 



mean current 



-\W'"- 



i being the current at each instant of the time T. 



(8) The effective current is the square root of the time average 

 of the square of the current. Thus 



effective current = 



s/{t/:- 



(9) The effective electromotive force is the square root of the 

 time average of the square of the electromotive force. Thus 



effective electromotive force = 4 / 1 "~ / ^"'^^ \ ' 



e being the actual electromotive force at each instant of the time T. 



(10) The impedance is the factor by which the effective cur- 

 rent must be multiplied to give the effective electromotive force. 

 Thus, in the case of a circuit of resistance R ohms, and self- 

 induction L quadrants in which a simple harmonic electromotive 



force of frequency ^^ is acting, impedance = V^^TIT*^. 



(11) In an accumulator the positive pole is that which is con- 

 nected with the positive pole of the machine when charging, and 

 from which the current passes into the external circuit when 

 discharging. 



The Committee are of opinion that they should be reappointed 

 with the addition of the name of Prof. J. Viriamu Jones. 



Report on the Present State of our Knowledge in Electrolysis and 

 Electro-chemistry. By Mr. IV. N. Shaw. 

 The following is an abstract : — 



I. General electrolytic phenomena. 



For a typical specimsn we cannot suppose an electrolytic 

 liquid otherwise than amixtureofsolutionsof chemical compound-, 

 though the amount of all but one constituent of the mixture 

 may be sd small as to be regarded merely as impurities which it 

 would not evei be possible to detect by ordinary chemical 

 means ; thus von Helmholtz said in his Faraday lecture he has 

 detected the polarization corresponding to the decomposition of 

 a quantity of water of the order i x lo-tl gramme, and Gore 

 (Proc. Roy. Soc, June 14, i838) has shown the effect of chlorine 

 upon the E.M.F. of a zinc platinum voltaic couple in distilled 

 water is such that the presence of one part of chlorine in 

 lODO million parts of water could be detected thereby. Pure 

 witer, since Kohlrausch's experiments, is now looked upon as 

 probably not conducting at all. Ratio of conductivity to that of 

 mercury = 071 x 10-10 at 2£°'5 C, and its sensitiveness to 

 small quantities of impurity approximated to that of the sense 

 of smell, since, when exposed in a room containing toba;co 

 smoke, its conductivity doubled in three hours. 



II. Laws and principles generally accepted. 



{a) The electro-magnetic action of the current passing throu:ih 

 an electrolyte is the same as if the electrolyte were replaced by 

 a metallic conductor of the same size and shape and o!" su:h 

 resistance that it could be substituted for the electrolyte without 

 altering the current in the rest of the circuit. 



ij}) There are electrolytes in which the conduction of electricity 

 from the electrode to the electrolyte, and agiin from the electro- 

 lyte to the electrode is entirely "convective" in the sense that 

 no electricity can pass into an electrolyte or out of it again 

 without causing a deposit of a certain n im'oer of constituent 

 ions at the anode and the opposite ions at the kathode, i.e. in 

 certain electrolytes no conduction takes place without chemical 

 decomposition. This holds for a large number of electrolytes, 

 possibly for all. It is not yet substantiated that it is true for all 

 electrolytes, but the evidence is continually accumulating in that 

 direction. 



(c) The conduction of electric currents through electrolytes 

 follows Ohm's law. Reference is made to C irystal's experi- 

 ments on metallic conduction, and Fitzgerald and Trouton's on 

 electrolytic conduction. 



One point is the experinental evidence for the deduction from 

 Maxwell's theory of light, that elec'rolytes being transparent 

 should behave as dielectrics for rapidly alternating electromotive 

 forces. There are two ways of approaching the q lestion — 



