504 EEPORT— 1879. 



publicly tried, in the illumination either of out-of-door spaces or streets, or of the 

 interior of public buildings or industrial works of various kinds. Since last year ' 

 many improvements have taken place, both in the machines for the generation of 

 the electric current, and also in the burners for utilising it. The actual require- 

 ments of practice, and especially the improved gas illumination in London and in 

 Paris, showed that electric lights of a more moderate illuminating power were 

 needed than were those afforded by the single-light machines of Siemens and of 

 Gramme. To the subdivision of the electric current for the production of an 

 increased number of light-centres of moderate illuminating power, and to a more 

 economical forni of burner, especially in the form of a ' candle ' instead of the more 

 delicate and expensive ' regulator,' has the attention of electricians been especially 

 directed. 



In the type of * Gramme ' machine used so far with the Jablochkoff candles 

 both in France and in this country, two separate machines have been required ; an 

 ' excitor ' to generate the current, to be passed on to the ' light ' machine for sub- 

 division into several distinct circuits. In the new form, though these two parts 

 are still separate, they compose but one machine ; which by a suitable arrangement 

 of the circuits may be made to support, with an expenditure of the same amount 

 of motive power, either the same number of lights as formerly, or, at will, the 

 number may be increased while luminosity of each is diminished, till the total 

 number of the light-centres is double that of the older machines ; while the aggre- 

 gate of the illuminating power remains about the same throughout. Thus, within 

 the writer's personal experience, a machine of the new type, which contained the 

 same amount of copper and iron as the old four-light machines, and absorbing 

 about the same amount of motive power, viz. 4| horse-power (net), could be made 

 to produce either four lights of nearly 600 candles each, or ten lights of about 240 

 candles. A larger machine of similar construction could, it was understood, feed, 

 either eight of the large, or twenty of the small lights, with an absorption of 

 rather under 10 horse-power. With the large lights, and the older type of machine 

 in use on the Thames Embankment, twenty lights require a net expenditure of 

 nearly 20 horse-power. 



With the Lontin machine an improvement in the same direction has taken 

 place ; the six-light machine of last year now producing twenty-four lights, each 

 of illuminating power somewhat similar to the small-sized lights just referred to. 

 In the De Meritens machine a somewhat increased productive power is the result of 

 a considerable simplification, and consequent economy, in the form of the steel 

 magnets employed. 



A new form of generator has entered the lists in the Thermo-electric pile of 

 M. Sudre, erroneously called by some the Clamond, from a former pile of this 

 name. The ' Sudre ' pile is a cylindrical hot-air furnace placed vertically, having 

 on its outside two sets of small flues, formed in cast-iron chambers ; and outside of 

 these a series of electric chains hang vertically, and are composed of small cubes 

 of an alloy of zinc and antimony, connected with each other by strips of tin, while 

 exterior to the cubes, and radiating from them, are placed vertically, like the leaves 

 of an open book, thin sheets of copper. The hot air from the top of the furnace is 

 forced downwards through one set of chambers, and up again through the outer 

 set, heating in its passage the zinc cubes which are placed against the flue, a strip 

 of asbestos only intervening ; while the copper plates act as the distributors of the 

 heat so acquired ; the difference of temperature between the heated back of the 

 zinc cubes and the outer edge of the copper plates being about 3 to 1. A double 

 pile of this construction, containing 3,000 zinc cubes or elements in each half, in 

 use in Paris for some months back, has a total electro-motive force of 218 volts, 

 which is equivalent to 120 Bunsen cells, and has a total resistance of 31 ohms. 

 This pile works two Serrin lamps very steadily and noiselessly, each giving a fair 

 moderate-sized light. The fuel consumed with the pile is coke ; about H hours 

 and 30 lbs. of coke being required to raise it to the required temperature, after 

 which 20 lbs. is the hourly consumption. 



1 See 'Present State of Electric Lighting,' in Minutes of Proceedings of the Bri- 

 tish Association, Dublin Meeting, 1878. 



