662 EEPOET— 1892. 



the author proposes to call the second \a.w of energetics, the law of conservation of 

 energy being the first law. This second law may be expressed in words in the 

 following way : A perpetuum mobile of the second order is impossible. By a 

 perpetuuui mobile of the second order is meant an engine by means of wliich 

 energy in equilibrium {e.g., heat of constant temperature, or electric energy of 

 constant potential) could be converted into work or some other form of energy. 



13. On a Delicate Calorimeter, By J. A. Harker, D.Sc, and 

 P. J. Hartog, B.8c. 



The authors have devised a calorimeter similar in principle to the Bunsen 

 ice-calorimeter, but in which the ice is replaced by pure solid acetic acid. Thi& 

 substance melts at about the normal temperature of rooms, and, moreover, yields a 

 considerably larger volume change per calorie than ice. The instrument will, it is- 

 hoped, prove specially useful for thermo-chemical measures with small quantities of 

 material, and for physiological work. 



14. Some Notes connected with the Electromotive Force of a Secondary 

 Battery. By Dr. J. H. Gladstone, F.B.S., and W. Hibbert. 



It has been recently shown by the autliors that the changes in E.M.F. in a 

 secondary battery depend mainly on the strength of the sulphuric acid that ia 

 against the working surfaces of the plates. If both plates be immersed in the 

 strongest acid the E.M.F. is 2'60 volts. On continuing the investigation the 

 authors have just found that, while lead against lead peroxide in pure water 

 gives 1-36 volt, lead in water against lead peroxide in the strongest sulphuric acid 

 gives 0-32 volt, and lead peroxide in water against lead in the strongest sulphuric 

 acid gives 0-89 volt. The sum of these is 2-57 volts, nearly the same as the figure 

 given above. By Lord Kelvin's thermo-electrical law it may be calculated that 

 when both plates are immersed in the strongest sulphuric acid the E.M.F. will be 

 2()2 volts, and when immersed in water 1-35 volt. This is in close agreement 

 with experiment. For intermediate strengths, however, theory and experiment 

 do not equally coincide. The authors are at present examining this point,'and 

 have found that the E.M.F. increases when the temperature rises, and they have 

 made a determination of the temperature coefficient, using a 14-7-per-cent. acid, 

 and find it 0-0136 volt per degree of temperature. 



