446 FKAGMENTS OF SCIENCE. 



between the naked carbons. M. cle Meritens has re- 

 cently brought out a new candle, in which the plaster 

 is abandoned, 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. 1 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 alto- 

 gether, 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 ad- 

 jacent 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 



1 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. 



