804 REPORT — 1895. 



When tests are made to check the efficiency and capacity of a battery, we can 

 place no reliance on the figures obtained from a single charge and discharge ; as a 

 rule no two consecutive discharges are identical, even when discharged with the 

 same current and down to the same voltage. In tables given in the paper the 

 first ten charges and discliai-ges from a new cell are recorded. These give a good 

 idea of the very various nature of results obtainable with slight differences of 

 charge. The figures show that the higher the voltage to which the cell is raised 

 on cliarge, the lower the etKciency, and also that a change of condition of charge 

 may increase or decrease the efficiencj^ and output to an extraordinary extent. 



The strength of the acid solution used has a great effect upon the behaviour of 

 a cell, also upon its life and voltage ; moreover, a weali solution has a high 

 resistance, which diminishes as acid is added, till a specific gravity of about 1-250 

 is reached, when any addition of acid rapidly increases the resistance ; the resist- 

 ance also rapidly increases as the temperature falls. Each type of cell works best 

 with a given strength of acid, but there are other most important points to be 

 considered, namely, that different strengths of the electrolyte have great efl'ect 

 both on the capacity of the cell and upon its voltage. 



Acid soluti(jns of specific gravity from Tl to 1-3 will vary the voltage as much 

 aslO per cent., and the highest capacities for various types of plates are obtained 

 with acid from specific gravity 1-2 to 1-3, and beyond these limits only a small 

 percentage of the maximum capacity can be obtained, and the curves of mean 

 voltage for diflei'ent strengths of acid bear a most interesting relation to the 

 various curves of capacity under the same conditions. 



The action upon plates when first erected and immersed in the electrolyte can, 

 to a great extent, be investigated by the fall and rise of its specific gravity, 

 various results being obtained from ijlates in diiierent states, and according to 

 whether they are left standing or immediately charged. The conclusions drawn 

 from many tests of this nature is, that fully formed positives with clean nejratives 

 are but little affected by standing, while partially formed positives and oxidised 

 negatives sulphate rapidly. 



Regarding the treatment of cells and their life the chief causes of destruction 

 are impure acid solution, too prolonged or excessive rates of discharge, insufficient 

 charging, overcharging, long periods of rest on open circuit without charging, and 

 allowing cells to remain a''ter complete discharge for many hours before recharging. 

 We find, therefore, that many causes influence the working and life of storage 

 batteries, and that many nf these can be varied at will ; the problem, therefore, is 

 to so combine all upeful effects, that the best possible article is produced with due 

 consideration to cost. 



In a secondary battery we have lead, sulphuric acid solution, and the resultant 

 compounds, and nothing else. The ideal cell is one that is indestructible, and this 

 being given, the first cost and weight, if kept within reasonable limits, are of 

 little moment. 



At the present moment the life of a cell is its value, and its death is brought 

 about by the disintegration of the active material. Now this disintegration is 

 what we have to stop, the material is as good as ever, for nothing is wasted, and 

 provided it were held in perpetual, firm, and good electrical contact with the 

 frame in such a manner that the free circulation and penetration of the acid were 

 not hindered, and the internal resistance not unduly increased, we should have 

 produced an ideal and indestructible cell. 



The_ author has discussed only a few of the many interesting features in 

 connection with secondary batteries, being results obtained iu practice. 



4. The Development of the Telephone Service in Agricultural Districts. 

 By Major-General Webber, C.B., R.E., M.Inst.C.E. 



On April 20, 1895, the ' Times ' published a letter from the author on the 

 subject iu which public attention was drawn to the probability that the telephone, 

 as well as light railways, might be beneficial to rural districts". 



