TRANSACTIONS OF SECTION G. 81 3' 



3. Electric Lighting in America.^ By Professor George Forbes, F.B.S. 



The author drew attention to the directions in which this industry has been 

 developed in America. The chief progress in central station work has been in' 

 three directions — (1) Arc lightinof ; (2) incandescent lamps with 3-wire system ; 

 (3) incandescent lamps with converters (Gaulard-Gibbs system). The number of" 

 arc lamps is now about 300,000. Every city in the States has some streets lighted 

 by arc lamps. The author described the methods of distribution, and gave the 

 reasons for slow progress in this country. There are at present 2| million incan- 

 descent lamps in use in the States. The author described the special features ot 

 the central stations, and drew conclusions as to the lessons to be learnt and applied 

 to practice in this country. 



4. On a System of Electrical Distribution.^ ^y Henry Edmunds. 



The problem of the distribution of electricity has considerably occupied the 

 attention of engineers, and several methods are in practical use, which may be 

 classitied under two heads — 



1. — Direct supply, which has the advantages of simplicity, and the employment 

 of currents of low tension ; but the disadvantages of requiring large conductors,, 

 and being limited to short distances from the source of supply. 



2. — Secondary generators, which are available over a larger area, and consider- 

 ably lessen the size of conductors, but, on the other hand, require to be more care- 

 fully insulated and protected, to prevent danger to life and property from the high 

 tension alternating currents employed. 



Both these systems are dependent upon the regular working of the machinery 

 at the central station ; any stoppage plunging a whole district into darkness, to 

 the great annoyance of consumers. To obviate this difficulty, secondary batteries 

 have been suggested, which would act as reservoirs, always leaving a margin to be 

 drawn upon in case of need. After reviewing the attempts which had been made 

 at New York and Colchester to utilise secondary batteries for the distribution of 

 electricity, and pointing out the causes of failure in each case, the ' Edmunds' 

 System of Electrical Distribution,' in actual use by the Cadogan Electricity Supply 

 Company in London, is described. 



By this system, groups of cells are placed in various portions of the district to 

 be lighted, each group being divided into a given number of sections. If the 

 group be divided into four sections it is arranged that three of these sections shall 

 be sufficient to supply the local demand, while the fourth is being charged by a 

 line from the central station. At given intervals, the section which has been 

 charged is removed from the main charging circuit, and switched into the local 

 one, through which it discharges itself, its place in the charging circuit being 

 taken by one of the other three, which, in its turn, is removed, and replaced by 

 the next, and so on. So each section is kept well charged, the charge never being 

 allowed to fall below a certain point. Thus the great desideratum is achieved"", 

 viz., constant supply, quite independent of any accident on the line or at the central 

 station. These changes are brought about automatically by an instrument called 

 a ' Disti-ibutor,' consisting of a revolving shaft carrying cams which, in their rota- 

 tion, cause levers to rise and fall, and thus make and break the necessary contact;', 

 at the proper intervals. A polarised switch is attached, to prevent the current 

 from entering the cells in the wrong direction, and also a voltage regulator, which 

 keeps the batteries out of the charging main when they are fully charged, and 

 connects them to it when they become exhausted, while a simple' form of meter 

 registers the amount of current consumed from day to day. 



This system oifers many important advantages. The" durability of the cells is- 

 much increased, owing to the favourable conditions under which they work. The 

 lamps give greater efficiency, through their being always run at an even pressure. 

 The conductors are of moderate dimensions, and do not require to be enlarged 



' Printed in extenso in Electrical Review, vol. xxiii. p. 275. 

 "^ Ibid. vol. xxiii. p. 284. 



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