, the insulating plaster is practically 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 naked 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. [Footnote:
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.] 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 work upon which
he was engaged might be, he would instantly turn aside from it to
seize and realise the ideas of a scientific man. He had an inventor's
power, and an inventor's delight in its exercise. The late Mr. Becker
possessed the same power in a very considerable degree. On the
Continent, Froment, Breguet, Sauerwald, and others might be mentioned
as eminent instances of ability of this kind. Such minds resemble a
liquid on the point of crystallisation. Stirred by a hint,