SCIENCE LETTER FROM PARIS. 39 



each other, in order to secure an equal light. To secure this necessary interval a 

 regulator was invented, worked either by the electric current or a clock move- 

 ment. Another improvement consisted in the use of a superior form of carbon; 

 but the most practical ameliora'ion was the invention of a machine to gener- 

 ate continuously, currents of electricity. This mechanical production of the 

 fluid, without a pile, was based on a singular phenomenon observed by Faraday 

 in 1832. When he brought a piece of soft iron into contact with a magnet 

 around which was wound a coil of copper wire covered with silk, there was an 

 instantaneous current of electricity developed in the wire, flowing, in one sense, 

 at the moment of contact, and, in a contrary, at the moment of removal. This 

 discovery has been ingeniously applied in the Bell telephone. It sufficed then 

 to turn such a coil before a piece of iron in order to obtain electric currents. 

 This is exactly how electric lamps and candles are fed at present, the magneto- 

 electric machine being turned by a little engine. Thus was dispensed with the 

 complicated and costly batteries of bottles, acids and deleterious vapors of the 

 laboratory. In many factories the electric machine is worked by a connection 

 with the ordinary motive power. 



For measuring the intensity of light, a carcel lamp in full power, consuming 

 about 1^ ounces of colza oil in an hour, is taken as unity. Now, the Voltaic 

 arc of Davy, condensed to a point, is too dazzling; it equals, in intensity, several 

 hundreds of carcel jets — it is a morsel of the sun. M. Fitzleau estimates, that, 

 tested by its photographic effects, sun is three-fifths stronger than electric light, 

 and M. Allard calculates that the Voltaic arc is six hundred times more intense 

 than the jet of the carcel lamp. To obtain the intensity of some of these elec- 

 tric arcs of light, it would be necessary to burn, in a vessel, one hundred and 

 seventy pounds of oil in an hour, or consume, during the same period of time, 

 the quantity of gas contained in a balloon having a diameter of thirty feet. 

 Such a quantity of light concentrated on so small a point was inconvenient — it 

 pains the eye. M. Plateau, of Brussels, lost his sight for having too long time 

 observed the effulgency of the electric light during his experiments. The next 

 difficulty to surmount was to distribute the light, to divide this brilliant point or 

 focus, and hang up at various distances on walls, like jets of gas, the luminous 

 morsels as stars. The young Russian engineer, Jablochkoff, has solved the 

 problem. He places two sticks of carbon parallel-wise, soldering them with a 

 special cement; this causes the electricity to flash at both the points of the car 

 bon — the heat instead of consuming the sticks volatilizes the cement, just as the 

 wick does the grease of a common candle. This is the "electric candle." The 

 carbon employed is very pure, so as not to affect the quality of light, and is pre 

 pared from graphite and sugar. The electric machine can thus have its currents 

 divided, in being distributed over several candles at once. The light thus pro- 

 duced is very beautiful and admirably fixed. M. Jablochkoff has also invented 

 a " condenser," by which the generated electricity can produce double its illumi- 

 nating effects along with improved quality of light. 



