Mr. R. H. M. Bosanquet on Practical Electricity. 249 



The cost of the construction is very considerable. I have 

 little doubt that they have cost me on the whole as much as 

 if I had bought them at the very high price charged. But 

 much of the expense could have been avoided. As it was, the 

 original construction cost under £2 per cell. About half the 

 outlay went to provide the wooden cases lined with lead. If 

 stoneware jars could have been procured, I think one third of 

 the original cost might have been saved. The " forming " of 

 the cells with the small power at my disposal was expensive. 

 I have not estimated the cost ; no doubt it could be done very 

 much more cheaply on the large scale. 



The best return I have ever obtained amounted to about 

 one half the power expended. This was obtained after a 

 charge of short duration, the cells running one Swan lamp. 

 The current and tension were measured at intervals. The 

 return was about 70 per cent, of the electrical charge taken, 

 and, as I judge, about half the total power expended. But 

 this is by far the best return I have ever obtained. As a rule, 

 the return is only a small fraction of the power expended. 



The other 9 cells are made with amalgamated plates of lead, 

 and " formed " by charging in opposite directions in the manner 

 practised with Plante batteries. These have less capacity than 

 the red-lead cells, and are troublesome to form ; but on the 

 whole I am inclined to prefer them for laboratory purposes 

 to home-made red-lead cells. They are much less trouble to 

 put together, and do not suffer from local action. 



Having cells of different kinds in the system is a great 

 inconvenience. When the red-lead cells have suffered from 

 local action, they increase their resistance ; and if systems of 

 balanced charging are employed, in which two or more cir- 

 cuits are used, a progressive change takes place in the distri- 

 bution of currents, which requires constant watching. It 

 should be a first principle that all the cells should be as similar 

 as possible. 



The red-lead cells have 11 plates in each cell, the others 15. 



With all their imperfections these cells are extremely useful 

 for laboratory purposes ; and as this was my object in con- 

 structing them, I am on the whole satisfied with their per- 

 formance. 



On charging Accumulators. 



Suppose that the accumulators are entirely without charge, 

 and the machine polarized rightly, having its residual magne- 

 tism such that the + terminal gives a positive current and the 

 — one a negative current. Then in charging we join + (or 

 oxygen) to +, and — (or hydrogen) to — , and all goes 



