1879 .] 
Notices of Books. 645 
kind of mechanism. In faCt, the candle simply consists of two 
cylindrical rods of carbon, about three-sixteenths of an inch in 
diameter, and from 6 % to 10 inches in length ; they are placed 
vertically side by side, with a space of three-sixteenths of an 
inch between them, which is filled with plaster-of-Paris. The 
latter is fused as the arc passes at the extremity of the candle, 
and this fusion absorbs 30 per cent of the eleCtric current ; 
moreover, the candle, if once extinguished, cannot be re-lighted. 
With a light equal to 760 candles, three inches of carbon are 
consumed per hour. Wilde has modified Jablochkoffis candle, 
by removing the insulating plaster-of-Paris. The lamps for 
lighting by incandescence alone have not at present made much 
way. 
In the fifth chapter the general principles of magneto and 
dynamo-eleCtric machines are fully discussed. Commencing 
with the machines of Pixii and Clarke, and ending with those of 
Gramme, Edison, and Lontin-Siemens machine is effective, but 
it can only be used with one Serrin’s 
said to give the following results : — 
or Siemens’s lamp. It 
Revolutions 
Illuminating power. 
Horse 
per minute. 
Standard candles. 
power. 
Weight. 
850 
1,200 
2 
280 
650 
6,000 
4 
420 
360 
14,000 
8 
1,288 
Useful tables showing the efficiency of different forms of 
dynamo-eleCtric machines are given on pp. 133, 136, 138, 140, 
143, and 149. The highest recorded efficiency of a dynamo- 
eleCtric machine is 38 per cent., while the efficiency of an 
ordinary steam engine in utilising the heat of the fuel does not 
exceed 20 per cent. The power expended by a dynamo-eleCtric 
machine in producing the light of one sperm candle is about 
equivalent, according to the author, to 90 lbs. falling through one 
foot in one minute. 
Some very interesting details as to the loss of production of 
the eleCtric light compared with gas are given in the ninth 
chapter. The cost in Paris is said to be double that of an 
equally intense street lighting by gas. One eleCtric light can 
usually be substituted for ten or twelve gas jets. The power 
absorbed is equal to one horse-power per candle. The subject 
of eleCtric carbons is discussed in the last chapter. Archereau 
mixes carbon with magnesia. Carre with different salts. 
Those of potash and soda at least double the length of the arc. 
Gaudoin introduces phosphate of lime and various silicates and 
borates ; others have coated the carbons with a deposit of metal 
such as nickel or copper, or have incorporated iron or copper 
in powder with the carbon. Gramme’s experiments with carbons 
saturated with nitrate of bismuth proved that a considerable 
increase of light resulted. 
