Paris, on the side of Earth that is now exposed to us, and then by
systematic search I soon located the response of your instrument.

"As our observations of Earth with projected light-rays have been
carried on for seven hundred years, it will be necessary to give you an
outline of our history and the progress of science covering that time.
This will not only be of interest as a forecast of your own world's
future, but will also prove of the greatest value to you, if you decide
to visit this planet, an undertaking which I am convinced lies within
your power."

His words wrung an exclamation of astonishment from my lips, but, as
though not wishing to be interrupted, he went on:

"Seven hundred years ago, a power derived from that substance known on
Earth as radium, was discovered on Mars. This power was found to be
capable of projecting light rays almost instantaneously through space
for inconceivable distances, at the same time preserving their integrity
to such a remarkable degree that they would reach the farthest planets
without diffusion or diminution. Thus my image, thrown upon the
instrument before me, is conveyed to Earth in light-waves by this flow
of super-radium with such tremendous speed as to be practically
instantaneous; these are received in your instrument, which is
responsive to the flow of super-radium, in the same condition as when
they left Mars, consequently depicting the image life-size.

"Having come in contact with another body in the heavens, this
outward-flowing current of super-radium is changed to an inward-flowing
current. In making this change it frees the light-waves it conveyed from
Mars, and retains the light-waves of the objects about it, which is