TBANSACTIONS OF SECTION G. 813 



batteries; others utilise secondary batteries or accumulators. One of the most 

 portable, compact, and convenient forms is that of Mr. Pitkin. It occupies a 

 cubical space of 59 cubic inches for two cells, and 86^ cubic inches for three cells, 

 weighing 5 lbs. 8 oz. and 7 lbs. 3 oz. respectively. The three-cell battery gives a 

 light equal to 2'5 candles immediately after removal from the charging source, 

 and lasts for nine or ten hours. It may also be used for other purposes that will 

 readily suggest themselves, and makes a very convenient reading lamp for railway 

 travelling, in conjunction with a small candle-power Edison-Swan lamp that 

 concentrates upon a book all the light required. The lamp is fixed in the focus of a 

 reflector whose surface is enamelled dead-white, instead of being bright-polished. 

 The light is thus much more uniformly distributed. It is, moreover, soft, absolutely 

 steady, and free from smell, or annoyance to one's fellow-passengers. It is lighted 

 instantly without any match, and can be rapidly replaced by a small coil of fine 

 platinum wire which, being raised to incandescence, serves for lighting a cigarette. 



4- On Improvements in Electric Safety Lamps. By J. Wilson Swan, M.A. 



See Reports, p. 496. 



5. Primary Batteries. By A. Rene Upward. 



After briefly reviewing the forms of primary battery from the simple elementary 

 cell to those of Daniell, Grove, Bunsen, &c., the author pointed out that the quantity 

 of current given by the combustion of a given weight of zinc is the same in all 

 batteries, but not the work done by the battery. The E.M.F. is proportional to 

 the net gain of power in the chemical reactions. 



The difficulties in the way of obtaining a perfect battery having been recapitu- 

 lated, the author's battery, the chief characteristics of which are the use of free 

 chlorine gas and the absence of polarisation in consequence of hydrogen not enter- 

 ing into the reactions, was described. The zinc being always in a solution of zine 

 chloride, no local action occurs ; there is no fear of mixing of liquids, as only one 

 liquid is used. The further advantages of this form of cell were enumerated as 

 follows : 



No fall in E.M.F., due to the solution becoming weaker, as the outer cells are 

 always full of practically pure chlorine gas ; no acids used in the cells (only pure 

 water added) ; no liquids to remove ; absence of smell or fumes ; no amalgamation of 

 the zincs ; no destruction of the terminals ; economy. 



The chlorine generator and gasholders were described, as well as the chlorine 

 cell itself, the battery, and the arrangements for the continuous automatic supply of 

 gas to the cells. 



6. The recent Progress in Secondary Batteries.^ 

 By Bernard Drake and J. Marshall Gorham. 



This paper gave an account of the various difficulties that existed some time 

 back when the writers first became connected with the Electrical Power Storage 

 Company, and dealt with the practical solution in each case. The writers stated 

 that the three most common sources of trouble were, first, the destruction of the 

 lead grid or conductor ; second, the buckling or warping of the plates ; third, the 

 falling out of the active material, the above being almost entirely confined to the 

 peroxide plates. The destruction of the grid both by local action and oxidisation 

 could easily be prevented by overcharging the cells in the first instance, whereby a 

 fine protecting coat of peroxide was formed on the surface of the conductor. If 

 this coating were reduced by the total discharge of the cells, a fresh surface of the 

 conductor would be attacked. The authors' experiments have shown that the life of 

 the lead grid is not proportional to the ampere-hours either put in or taken out of 



' Published in extemo in Engineering, vol. xlii. p. 302. 



