But the long and the short
of it is that when a current of electricity passes through a wire there's
a lot of magnetism present round that wire; and if you put another wire
parallel to, and within what we call its magnetic field--why then, the
second wire will also become charged with electricity."
"On its own account?"
"On its own account."
"Then let's see if I've got it correctly. Miles off, at Poole, or wherever
it is----"
"It will be anywhere in ten years."
"You've got a charged wire----"
"Charged with Hertzian waves which vibrate, say, two hundred and thirty
million times a second." Mr. Cashell snaked his forefinger rapidly through
the air.
"All right--a charged wire at Poole, giving out these waves into space.
Then this wire of yours sticking out into space--on the roof of the house
--in some mysterious way gets charged with those waves from Poole----"
"Or anywhere--it only happens to be Poole tonight."
"And those waves set the coherer at work, just like an ordinary telegraph-
office ticker?"
"No! That's where so many people make the mistake. The Hertzian waves
wouldn't be strong enough to work a great heavy Morse instrument like
ours. They can only just make that dust cohere, and while it coheres (a
little while for a dot and a longer while for a dash) the current from
this battery--the home battery"--he laid his hand on the thing--"can get
through to the Morse printing-machine to record the dot or dash.
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