pressions was gradually gathering.

"It is not so pumped up," said Sam. "The pipes were used, not because
they were pipes, but because they were metal, and therefore good
conductors."

"But you haven't told us about the beautiful experiments yet," murmured
Letta, a little impatiently.

"I'm coming to them, little one," said Sam. "One battery exhibited the
power as well as the beauty of that mysterious force which we call
electricity. It was the large Grove battery. A current passed from it
to copper wires, in a certain manner, produced a dazzling green light,
and the copper melted like wax. With silver a still brighter and purer
green flame was the result. With platinum an intense white light was
given off, and the molten metal fell in globules of exceeding
brilliancy. With iron lovely coruscations were exhibited, the boiling
vapour flying and burning in all directions; and a platinum wire three
feet long was in an instant melted into thousands of minute globules.
All this showed the power of electricity to produce intense heat when
resistance is opposed to its passage."

"It is remarkably human-like in that respect," said Captain Rik, in an
under-tone.

"Then its power to produce magnetism," continued Sam, "was shown by Lord
Lindsay's huge electro-magnet. This magnet, you must know, is nothing
but a bit of ordinary metal until it is electrified, when it becomes a
most powerful magnet. But the instant the current is cut off from it,
it ceases to be a magnet. If you understood much about electricity,"
said Sam, looking round on his rapt audience, "I might tell you that it
is upon this power of making a piece of iron a magnet or not at
pleasure, that depend the Morse and Digne telegraph instruments; but as
you don't understand, I won't perplex you further. Well, when a piece
of sheet copper was passed between the poles of Lord Lindsay's giant
magnet, it was as difficult to move as if it had been sticking in
cheese--though it was in reality touching nothing!--influenced only by
attraction." ("That beats your power over Sam, Madge," whispered Robin.
"No it doesn't," whispered Madge in reply.) "Then, one most beautiful
experiment I could not hope to get you to understand, but its result
was, that a ten-gallon glass jar, coated inside and out with perforated
squares of tinfoil, was filled with tens of thousands of brilliant
sparks, which produced so much noise as completely to drown the voices
of those who d