TRANSACTIONS OF SECTION G. 707 



these currents, on being 1 passed backwards and forwards between them, are 

 gradually augmented to a very considerable decree, the result being a small, 

 economical, and much more powerful machine, termed " dynamo-electric " (electro 

 magnets being used) than are the previously described "magneto-electric'' ones 

 (where permanent magnets were employed). The best known machines of this 

 class are the " Siemens " and the " Gramme " in this country, and in the United 

 States the " Brush " and the " Wallace-Farmer." 



The third and present stage of electric lighting is that of the divisibility of the 

 lisrht, i.e., the production of a number of lights from one machine. This has been 

 effected in practical use by Lontin with his double-machine, and the double-Gramme 

 feeding the well-known Jablochkotf candles. With these last, an Alliance machine 

 was at first used, but latterly ML Gramme devised his second machine, and which 

 has the appearance of the already existing Lontin. 



In the double machine (of Lontin, and also in that of Gramme), the current 

 is created in a small one, termed the "generating" one, and passed on in one con- 

 tinuous direction current to the larger or " dividing " one ; on the outer envelope of 

 which it is received divided into a number of distinct circuits, which may be 

 coupled together at will. The Lontin machines, so far, have produced twelve 

 circuits from such a machine with a maximum, in lengthened use, of thirty lights ; 

 while the Gramme generally works with four circuits and feeds sixteen Jablochkotf 

 candles. 



Of the lamps or regulators, those most in use for single lights are the Serrin and 

 the Siemens ; while, where many lights are producid, the Jablochkotf" candles" and 

 the divers forms of Lontin regulators are available. The Jablochkotf candle con- 

 sists of the two carbons placed vertically side by side, with an insulating layer of 

 plaster of Paris between them ; which is an attempt to dispense with the delicate 

 mechanism of the regulating apparatus, and attended with only very moderate success. 

 The arrangements of the Lontin regulators are very ingenious, and very sensitive ; 

 some of the forms may be placed in any position whatever and be used with 

 currents, either continuous or alternating in direction. 



The very careful preparation of the carbon-sticks between which the electric 

 light is produced is at present receiving attention, so as to render their composi- 

 tion as homogeneous as possible, and thereby to reduce the flickerings in the light 

 produced. 



The motor power to cause the necessary rate of motion to the revolving electro- 

 magnet or induction coil (generally between 400 and 1000 revolutions per minute) 

 may be either hydraulic power in the form of a turbine or otherwise, or a gas 

 engine, or a steam-engine. But, whichever of the three is used, extreme regularity 

 of motion is an absolute necessity ; otherwise any want of steadiness in running 

 is productive of flickering in the electric light. Therefore, where possible, the 

 engine performing this duty should be special for the purpose, and not have other 

 work to do at the same time. 



A most important consideration in connection with electric lighting is, apart from 

 the prime cost of the machines, motor, lamps, &c, the amount of the working expenses 

 thereof, and chiefly the proportion and cost of the motor power to the amount of 

 light produced. A rough estimate of this is given by the designers of these 

 machines as one indicated horse power for each light of 1000 standard candles. 

 Where the number of lights is considerable, this may hold good ; but for a few, or for 

 single lights, a larger allowance for engine power should be made, even when running 

 ordinarily, and without the sudden and severe strains to which they are exrosed. 

 Many manufacturers at and near Paris, at Rouen, and at other places in France, 

 have made use of electric lighting in spinning and weaving sheds, in iron works, 

 &c, for the last two years, and they generally consider that they have been sup- 

 plied with a vastly augmented amount of illumination at considerably less than 

 one-half the cost of the previous, and much poorer one, by means of gas. 



Though electricity may replace gas lighting to some extent in the illumination 

 of large areas, and in certain manufactures, yet it cannot pretend to trench upon 

 the special, and the most extensive field for the use of gas, the lighting of private 



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