444 FRAGMENTS OF SCIENCE. 



the naked carbons. M. de Meritens has recently 

 brought out a new candle, in which the plaster is aban- 

 doned, while between the two principal carbons is placed 

 a third insulated rod of the same material. With the 

 small de Meritens machine two of these candles can 

 be lighted before you; they produce a very brilliant 

 light.* In the Jablochkoff candle it is necessary that 

 the carbons should be consumed at the same rate. 

 Hence the necessity for alternating currents by which 

 this equal consumption is secured. It will be seen 

 that M. Jablochkoff has abolished regulators altogether, 

 introducing the candle principle in their stead. In my 

 judgment, the performance of the Jablochkoff candle 

 on the Thames Embankment and the Holborn Viaduct 

 is highly creditable, notwithstanding a considerable 

 waste of light towards the sky. The Jablochkoff 

 lamps, it may be added, would be more effective in a 

 street, where their light would be scattered abroad by 

 the adjacent houses, than in the positions which they 

 now occupy in London. 



It was my custom some years ago, whenever I needed 

 a new and complicated instrument, to sit down beside 

 its proposed constructor, and to talk the matter over 

 with him. The study of the inventor's mind which 

 this habit opened out was always of the highest interest 

 to me. I particularly well remember the impression 

 made upon me on such occasions by the late Mr. Darker, 

 a philosophical instrument maker in Lambeth. This 

 man's life was a struggle, and the reason of it was not 

 far to seek. No matter how commercially lucrative 



* The machine of M. de Meritens and the Farmer- Wallace 

 machine were worked by an excellent gas-engine, lent for the 

 occasion by the Messrs. Crossley, of Manchester. The Siemens 

 machine was worked by steam. 



