C. GENERAL PHYSICS. ]61 



being very economical, and applicable for a great many pur- 

 poses from which it is now debarred on account of its un- 

 certainty and want of precision. By the old method the 

 electric current was passed between two points of charcoal, 

 each attached to a copper wire connected with an electro- 

 magnetic machine. The disadvantages of this arrangement 

 Avere that a separate machine was required for each light, 

 and these were very difficult, if not impossible, of regulation, 

 and liable to constant interruption, owing to the rapid con- 

 sumption of the charcoal points from exposure to air. 



By the newly invented method of Mr. Eadiguin, only one 

 piece of charcoal or other bad conductor is required, which, 

 beingr attached to a wire connected with an electro-magnetic 

 machine, is placed in a glass tube, from which the air is ex- 

 hausted, and replaced by a gas which, even at a high tem- 

 perature, will not combine chemically with the charcoal. 

 This tube is then hermetically sealed, and the machine being 

 set in motion by means of a small steam-engine, the charcoal 

 becomes gradually and equally heated, and emits a soft, 

 steady, and continuous light, which, by a most simple con- 

 trivance, can be strengthened or weakened at the option of 

 those employing it, its duration being dependent solely on 

 the electric current, which, of course, will last as long as the 

 machine is kept in motion. 



Taking into consideration the fact that one machine, worked 

 by a small three-horse-power engine, is capable of lighting 

 many hundreds of lanterns, it is evident what an enormous 

 advantage and profit could be gained by the illumination of 

 streets, private houses, public buildings, and mines with the 

 new electric light. In the latter it must prove invaluable, 

 as no explosion need ever be feared from it ; and these 

 lanterns will burn equally as well under water as in a 

 room. 



Without mentioning the many advantages this mode of 

 illumination has over gas, which, by its unpleasant odor and 

 evaporation, is slowly poisoning thousands of human beings, 

 and from which explosions are frequent, we can state that, 

 by calculations made, this electric light can be produced at 

 a fifth of the cost of coal gas. 



The journal of the Society of Arts promises soon to place 

 before the public more complete particulars of this great im- 



