182 KANSAS CITY REVIEW OF SCIENCE. 
each on three successive days, do not show a much better result. In this case 
the weight of the battery plates only is given, and that eighty-one pounds. Re- 
ducing the results proportionally for batteries whose plates weigh forty-eight 
pounds, I find that by the experiments of Professors Ayrton and Perry each cell 
of this weight should give 853,333 foot-pounds of energy. 
This again is less than half the amount of energy which I have repeatedly 
obtained from your battery. 
Passing next to the efficiency of your batteries as regards their delivery of 
nearly the same current as was used to charge them, I have found that the loss 
in this relation is less than 10 per cent. In other words, in my experiments I 
have obtained from these batteries 90 to 91 per cent, of the current used to 
charge them. This far exceeds the results obtained by M. Tresca with the Faure 
batteries. 
Tresca reports that he recovered only 60 per cent, of the current used to 
charge the battery, and Ayrton and Perry found the loss in charging and dis- 
charging to be '* not greater than 18 per cent." 
In this, however, is included the loss due to the fall of electro-motive force 
in the discharge as compared with the charge. This I find to be on the average 
less than -^-^ of a volt, which would bring the total loss of available energy ob- 
tained from the battery, as compared with that expended in charging it, to 18 per 
cent. 
Lastly comes the very important question as to the retention of charge dur- 
ing a long time. To test this I charged three cells and locked them in a closet 
on February ist, where they remained until February i6th, when I began dis- 
charging them at the rate of 32 amperes, continuing this rate of discharge on the 
next day. I thus obtained 266.7 ampere hours of current. 
Comparing this with the 286.5 ampere hours of current obtained from the 
other cells which I discharged soon after charging them, shows a loss of 7 per 
cent, caused by standing for sixteen days. 
The above measurements and comparisons show that this storage battery 
has attained a degree of efficiency which will render it applicable to a number of 
uses. Thus, for example, on steam-boats, by the use of such storage batteries, the 
irregular and occasionally interrupted motion of the main engine might operate a 
relatively small dynamo-electro machine so as to charge the batteries during the 
entire twenty-four hours, and the current from these batteries would then supply 
light with perfect steadiness during the relatively brief time in which it is required. 
In this way the cost of supplying and running a special and large engine, which 
would be needed for operating the same lights directly without the storage bat- 
tery, would be avoided, and also the necessity for extreme steadiness in running 
the dynamo, and all risks of extinction of the lights, from a momentary interrup- 
tion of motion in any part of the machinery would be removed, as the battery 
would secure an absolutely steady and continuous supply of current no matter 
how little regular might be the action of the engine or dynamo-electric machine. 
Again, in larger buildings the engine used to operate the elevator or to do 
