was converted into heat, in others into sound, in others into work. At
this part of the lecture reference was made to the work of Prof. Ayrton
and his pupils at Cowper street (City and Guilds of London Institute
Classes). They measure (1) the gas consumed by the engine, (2) the
horse-power given to the dynamo machine, (3) the current in the
circuit in webers, and (4) the resistance of the circuit. Thus exact
calculations can now be made as to the horse power expended in any
part of the circuit, and the light given out in any given period by
an electric lamp. The dynamometers used in these measurements were
described, but at present, in some cases, the description given is for
various reasons incomplete, so that we shall take a future opportunity
of writing of these instruments. To measure the light a photometer,
constructed by Profs. Ayrton and Perry, is used, which obviates the
necessity of large rooms, and enables the operator to give the intensity
in a very short period of time. A number of measurements of the
illuminating power of an electric lamp were rapidly made during the
lecture with this photometer. By means of a small dynamo machine, driven
by an electric current generated in the Adelphi arches, a ventilator,
a sewing machine, a lathe, etc., were driven; in the latter a piece of
wood was turned. "What," said the lecturer, "do these examples show
you?" "They show that if I have a steam-engine in my back yard I can
transmit power to various machines in my house, but if you measured the
power given to these machines you would find it to be less than half
of what the engine driving the outside electrical machine gives out.
Further, when we wanted to think of heating of buildings and the boiling
of water, it was all very well to speak of the conversion of electrical
energy into heat, but now we find that not only do the two electrical
machines get heated and give out heat, but heat is given out by our
connecting wires. We have then to consider our most important question.
Electrical energy can be transmitted to a distance, and even to many