‘Then, to begin with a simple example in ordinary life, you know what telepathy is?’
‘Of course, but tell me.’
‘Suppose Jones is thinking of Smith, or rather of Smith’s sister. Jones is dying, or in a row, in India. Miss Smith is in Bayswater. She sees Jones in her drawing-room. The thought of Jones has struck a receiver of some sort in the brain, say, of Miss Smith.
But Miss Smith may not see him, somebody else may, say her aunt, or the footman. That is because the aunt or the footman has the properly tuned receiver in her or his brain, and Miss Smith has not.’
‘I see, so far—but the machine?’
‘That is an electric apparatus charged with a message. The message is not conducted by wires, but is merely carried along on a new sort of waves, “Hertz waves,” I think, but that does not matter. They roam through space, these waves, and wherever they meet another machine of the same kind, a receiver, they communicate it.’
‘Then everybody who has such a machine as Mr. Macrae’s gets all Mr. Macrae’s messages for nothing?’ asked Lady Bude.
‘They would get them,’ said Merton. ‘But that is where the artfulness comes in. Two Italian magicians, or electricians, Messrs. Gianesi and Giambresi, have invented an improvement suggested by a dodge of the Indians on the Amazon River. They make machines which are only in tune with each other. Their machine fires off a message which no other machine can receive or tap except that of their customer, say Mr. Macrae. The other receivers all over the world don’t get it, they are not in tune. It is as if Jones could only appear as a wraith to Miss Smith, and vice versa.’
‘How is it done?’
‘Oh, don’t ask me! Besides, I fancy it is a trade secret, the tuning. There’s one good thing about it, you know how Highland landscape is spoiled by telegraph posts?’