a certain machine which he had conceived, but not as yet perfected,
it would be possible to complete all existing systems of aerial
communication, and enormously to simplify their action and enlarge their
scope. His instruments, which were wireless telephones--aerophones he
called them--were to be made in pairs, twins that should talk only
to each other. They required no high poles, or balloons, or any other
cumbrous and expensive appliance; indeed, their size was no larger than
that of a rather thick despatch box. And he had triumphed; the thing was
done--in all but one or two details.

For two long years he had struggled with these, and still they eluded
him. Once he had succeeded--that was the dreadful thing. Once for a
while the instruments had worked, and with a space of several miles
between them. But--this was the maddening part of it--he had never been
able to repeat the exact conditions; or, rather, to discover precisely
what they were. On that occasion he had entrusted one of his machines to
his first cousin, Mary Porson, a big girl with her hair still down her
back, rather idle in disposition, but very intelligent, when she chose.
Mary, for the most part, had been brought up at her father's house,
close by. Often, too, she stayed with her uncle for weeks at a stretch,
so at that time Morris was as intimate with her as a man of eight and
twenty usually is with a relative in her teens.

The arrangement on this particular occasion was that she should take the
machine--or aerophone, as its inventor had named it--to her home. The
next morning, at the appointed hour, as Morris had often done before, he
tried to effect communication, but without result. On the following day,
at the same hour, he tried again, when, to his astonishment, instantly
the answer came back. Yes, as distinctly as though she were standing by
his side, he heard his cousin Mary's voice.