f course, but unlikely, that Mars would have
intelligent inhabitants still ignorant of the telescope. It was also
possible that their senses would be different from ours--that, if they
saw at all, it would be with a different part of the spectrum. Father
took the chance. And he succeeded.

"The call was simple: merely three flashes of light, repeated again
and again. We used a portable searchlight, mounted on a motor-truck,
such as is used in the army. The three flashes meant that we were on
the third planet of the solar system. The answering call, from the
fourth planet, should be four flashes, of course.

"For three nights we kept signaling. One of the men watched the
motor-generator, and I operated the searchlight, swinging it on Mars
and off again, to make the flashes. Dad kept his eye screwed to the
telescope. Nothing happened and he got discouraged. I persuaded him to
keep on for another night, in case they hadn't seen us at first; or
needed more time to get their searchlight ready.

"And on the fourth night poor Dad came out of the observatory,
shouting that he had seen four flashes."

* * * * *

Dan gasped, speechless with astonishment. "Then that machine, with the
needle pointing at Mars, and the green flashes, and the thing that
jumped at me--"

Helen waved a white hand for silence. "Just keep cool a minute! I'm
coming to them.

"The four flashes just began it. In a few days Dad and the Martians
were communicating by a sort of television process. He would mark off
a sheet of paper into squares, blacken some of the squares to make a
picture or design, then have me send a flash for each black square,
and miss an interval for each white one, taking them in regular order.
The Martians seemed to catch on pretty soon; in a few days Dad was
receiving pictures of the same sort.

"Rather a slow way of communication, perhaps. But it worked better
than one might think at first. In a month Dad had received
instructions for building a small machine like that big one on the
hill. It is something like radio--at least it operates with vibrations
in the ether--but it's as much ahead of our radio as an airplane is in
advance of a fire-balloon. I understand a good bit about it, but I
won't try to explain it now.

"And in the next three years Dad learned no end of things from the
people on Mars. One queer thing about it was, that they never let us
see them on the television apparatus, no