TRANSACTIONS OF SECTION A. 

 The mean of experiments 23-45 is also given. 



781 



The Density varied from 1-155-1-167, a les.s range than when charging at 

 constant P.D. 



Resistances. — 



Beginning of charge 

 00038 ohm. 



End of charge Beginning of discharge End of discharge 

 0-0077 ohm. 00041 ohm. 00034 ohm. 



The shapes of the curves of charge and discharge at constant current are very- 

 well known, and need not be commented upon here. 



Comparison of the two Methods of Charging. 



What we have to compare in order to get an insight into the relative advantages 

 and disadvantages of the two methods are : 



The discharge capacity, or the energy we can get out of the cell. 

 The time needed for charging. 



The storage efficiency or ratio of '^*"' ^'^^^^ "^^^ 



watts put in 

 4. The life of the cell. 



The first three are put into tabular form below, and we thus see that by charging 

 at constant potential the time of charging is le.ss than half that which is required 

 if we charge at constant current, and that the capacity is 30 per cent, greater if 

 the first method is employed, but that the energy efficiency is 10 per cent. less. 



This loss of efficiency is probably due to the excessive heating caused by the 

 large initial currents. 



With regard to the life of the cell when charged at constant P.D., we can only 

 say that after more than fifty charges and discharges the cell seemed in no way 

 the worse. 



The plates were not at all bent, neither was the amount of sediment at the 

 bottom of the cell notably greater than at the beginning of the tests. 



