May 25, 1888.] 



SCIENTIFIC NEWS. 



+83 



volts, and as that of the current in the house is required 

 at 24 volts, it is sufficient to use 12 cells at a time, 

 the thirteenth being kept in reserve. The E. M. F of each 

 cell is very easily ascertained by thecell tester (shewn in fig. 

 2) designed by the Electrical Power Storage Company, and 



the rod being insulated. When used the rod is simply 

 laid across the cell with one hand, whilst the voltmeter is 

 held in the other and observed, each brass tube resting on 

 a lead strip. The specific gravity of the acid in the cells 

 is ascertained by the usual acidometer (shewn in fig. 3). 



^ 



^^.: >:::-'>>'^ 



-Accumulator Cells, 



Fig. 3,— Acidometer. 



Fig. 



-Cell Tester. 



fully described in Sir David Salamons' handbook on the 

 " Management of Accumulators." In this apparatus there 

 is a portable voltmeter, and to this are attached two 

 wires fastened to a wooden rod, which has roughened 

 brass tubes fixed on it at each end, the middle portion of 



A record of the readings of the voltmeter and of the 

 acidometer, as well as of the gas meter attached to the 

 engine, is entered in a book at the beginning and end of 

 each day's charging. A little practice renders the whole 

 process extremely simple, especially as the colour and 

 condition of the acid and plates can be clearly seen 

 through the glass cells. 



The chief feature of novelty in General Webber's 

 arrangements is, that all his glow lamps are of only 

 5-candle power each. In this way he can get great 

 subdivision of light with an economical consumption of 

 current. There are 62 points in the house, to most of 

 which moveable lamps can be connected by short flexible 

 cords, but the average number of lamps in use at one 

 time is only about 20. To prevent over-discharge of the 

 accumulators, not more than 30 lamps should be 

 lighted at once, and near the accumulators is an auto- 

 matic discharging cut-out, which, instead of cutting tif 

 the current, rings a bell in the house if more than 30 

 are in use. Since October last it has been sufficient to 

 charge the cells twice a week from 8 to 10 hours on 

 each occasion, with one extra day's charging when the 

 discharge has been abnormal. An intelligent lad, who 

 is paid 3s. for each actual day's working of the plant, 

 has sole charge of the whole. As a precaution, there is 

 an automatic cut-out made by the Electrical Power 

 Storage Company, which cuts off the dynamo from thr 



