ELECTRIC LIGHTING. 



paper. Extended trial showed that 

 the paper strips varied greatly in 

 density, and hence became un- 

 equally heated when the current 

 was passed through them, with the 

 result of soon becoming disinte- 

 grated. The bamboo is much more 

 homogeneous, and has therefore 

 been adopted. For general use, it 

 is intended to make the lamps of 

 two sizes, the carbon strip in one 

 being five inches in length and in 

 the other three. Eight lights of 

 sixteen candles each of the former, 

 or sixteen lights of eight candles 

 each of the latter, can be main- 

 tained, Mr. Edison states, with an 

 expenditure of one actual, or one 

 and a quarter indicated, horse- 

 power. As in the best gas-engines 

 twenty-five feet of gas an hour will 

 give an actual horse-power, and as 

 this amount of gas will only sup- 

 ply five lights of sixteen candles 

 each, there appears to be a gain 

 in the ratio of eight to five, in first 

 converting the energy of the gas 

 into electricity and this into light, 

 over burning the gas direct as an 

 illuminant. Electricity has, how- 

 ever, on this basis, a somewhat 

 greater advantage than is shown 

 by the figures, in that the lamps 

 will give the full sixteen - candle 

 light as long as they last, while 

 gas-burners gradually deteriorate, 

 with a consequent lessening of the 

 light. The life of the carbon strip 

 varies greatly with the different 

 samples. Some will last but from thirty to 

 forty hours, while others have remained intact 

 as many as twelve hundred, the average of a 

 large number of trials being three hundred. 



An incandescent lamp, quite similar to that 

 of Mr. Edison, shown in Fig. 1, and a regulat- 

 ing apparatus, have been brought out quite re- 

 cently by Mr. H. S. Maxim, the inventor of the 

 arc lamp which bears his name. The carbon 

 strip, made from cardboard or wood, is bent 

 in the form of the letter M, or a Maltese cross, 

 instead of a simple loop. The globe contains a 

 rarefied atmosphere of gasoline, the object of 

 which is to build up the thinner parts of the 

 carbon by the deposition upon them of the free 

 carbon of the dissociated vapor. This action 

 takes place within a few hours after the lamps 

 are started burning, so that the result is an in- 

 candescent strip in an atmosphere of hydrogen. 

 The inventor states that the carbon is rendered 

 very dense and homogeneous by this process, 

 and its durability considerably increased. The 

 sealing is done by inclosing the wires in a semi- 

 elastic cement, instead of fusing them into the 

 glass. The regulator, which is designed to 

 automatically vary the current in accordance 

 with the number of lamps in circuit, is of quite 



FIG. 1. 





simple construction, and has been found to be 

 fairly satisfactory in use. It operates by in- 

 creasing and decreasing the intensity cf the 

 field magnets of the machines furnishing the 

 current, through the medium of an electro- 

 magnet plnced in the lamp-circuit. When any 

 considerable number of lamps are operated, 

 the current is furnished by a number of gen- 

 erators, whose magnetic fields are maintained 

 by a separate machine, and, in order to vary 

 the current furnished the lamps, it is only ne- 

 cessary to increase or decrease the current sup- 

 plied by the latter. This is done by shifting 

 the commutator-brushes to and from the neu- 

 tral points, the current varying with each change 

 in their position. The mechanism by which 

 this result is accomplished is shown in Fig. 2. 

 The train of gearing in the lower portion of 

 the apparatus consists of two ratchet-wheels, 

 on the shaft of each of which is a spur-wheel, 

 meshing into ah intermediate one. This latter 

 is mounted uppn a shaft which moves the com- 

 mutator-brushes of the machine, through the 

 medium of the bevel-gearing to the right. Be- 

 tween the ratchet-wheels there is a reciprocat- 

 ing pawl, operated by the machine. In its 

 normal position this pawl moves freely between 



