the others, while the coupling of two
Grammes, or of two Siemens together, here effected for the first time,
was followed by a very great augmentation of the light, rising in the
one case from 6663 candles to 11,396, and in the other case from 6864
candles to 14,134. Where the arc is single and the external
resistance small, great advantages attach to the Siemens light. After
this contest, which was conducted throughout in the most amicable
manner, Siemens machines of type No. 2 were chosen for the Lizard.
[Footnote: As the result of a recent trial by Mr. Schwendler, they
have been also chosen for India.]

*****

We have machines capable of sustaining a single light, and also
machines capable of sustaining several lights. The Gramme machine,
for example, which ignites the Jablochkoff candles on the Thames
Embankment and at the Holborn Viaduct, delivers four currents, each
passing through its own circuit. In each circuit are five lamps
through which the current belonging to the circuit passes in
succession. The lights correspond to so many resisting spaces, over
which, as already explained, the current has to leap; the force which
accomplishes the leap being that which produces the light. Whether
the current is to be competent to pass through five lamps in
succession, or to sustain only a single lamp, depends entirely upon
the will and skill of the maker of the machine. He has, to guide him,
definite laws laid down by Ohm half a century ago, by which he must
abide.

Ohm has taught us how to arrange the elements of a Voltaic battery so
as to augment indefinitely its electromotive force--that force,
namely, which urges the current forward and enables it to surmount
external obstacles. We have only to link the cells together so that
the current generated by each cell shall pass through all the others,
and add its electro-motive force to that of all the others. We
increase, it is true, at the same time the resistance of the battery,
diminishing thereby the quantity of the current from each cell, but we
augment the power of the integrated current to overcome external
hindrances. The resistance of the battery itself may, indeed, be
rendered so great, that the external resistance shall vanish in
comparison. What is here said regarding the voltaic battery is
equally true of magneto-electric machines. If we wish our current to
leap over five intervals, and produce five lights in succession, we
must invoke a suff