680 F11AQMKNT8 0V SCtKNCtt. 
piece is immediately dissipated or removed by the current, 
the passage of which ouce established is afterward main- 
tained. The carbons gradually waste, while the substance 
between them melts like the wax of a candle. The com* 
parison, however, only holds good for the act of melting; 
for, as regards the current, the insulating plaster is practi- 
cally inert. Indeed, as proved by M. Rapieff and Mr. 
Wilde, the plaster may be dispensed with altogether, the 
current passing from point to point between the nuked 
carbons. M. de Meritens has recently 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. * 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 Jabloch- 
koff candle on the Thames Embank men't and the Hoi born 
Viaduct is highly creditable, notwithstanding a consider- 
able waste of light toward 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 work upon which 
* 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. Crosley, of Manchester. The Siemens machine was worked 
by steam. 
