326 



SCIENCE, 



[Vol. XIV. No. 354 



dynamos are started at 2 p.m. and work till midnight, — a working 

 day of ten hours, — thus rendering the ordinary electric-light plant 

 efficient the whole day. 



There is another field in which accumulators take an active part, 

 — that of long-distance lighting, now so successfully occupied by 

 the alternating converter system, in which the high-potential cur- 





type, is proportional to the number and size of its plates ; its rate 

 of discharge depending upon the number of plates and the effec- 

 tive surface of each, while the time of such discharge varies with 

 their thickness. Although there are no obvious theoretical reasons 

 why a single cell of accumulator should not be made sufficiently 

 large to possess any desired capacity, there are mechanical con- 



rents on the main lines are converted into those of lower potential 

 before entering buildings for use. An accumulator is a chemical 

 converter ; and, now that the questions of cost and durability are 

 practically solved, the accumulator is likely to find an application 

 for this converting process. 



There is, of course, a practical loss every time energy is trans- 



siderations which make it advisable to limit the dimensions of a 

 cell to the extent that it may be conveniently portable, Therefore, 

 when higher rates or longer discharges than an ordinary cell will 

 give are demanded, two or more cells must be connected in par- 

 allel. 

 When two or more series of cells connected in parallel are to be 



J^ 



Fig. 3- 



formed from one form to another, and this loss is greater the more 

 rapid the rate of charge and discharge of a storage-battery ; but 

 this loss, added to the cost of the accumulators, is not believed to 

 be enough to counterbalance the advantages already mentioned. 



Generally speaking, the total current capacity, expressed in 

 ampere hours, of a single cell of accumulator of the lead lead-oxide 



charged at the same potential, it is evident, that, unless each series 

 is in precisely the same state in respect to residual charge, there 

 will be a difference in their electro-motive forces, and in conse- 

 quence less current will flow in those series having higher poten- 

 tials than in others. While the larger current flowing into the 

 less charged cells will have a tendency to bring up their potentials 



