The idea of a radio signal to the moon may sound fantastic, but is easily within the range of possibility, says Dr. A. Hoyt Taylor, Chief of the Radio Division of the United States Naval Research Laboratories at Washington, who plans such an attempt in the near future. "We have reason to expect a good chance of getting the signal back in a time interval of slightly less than three seconds," said Dr. Taylor. To be exact, a radio signal should be reflected back to earth in a time interval of 2.8 seconds, this being the necessary elapsed time for it to carry the 250,000 miles to the moon and return at its speed of 300,000 kilometers, or 186,000 miles per second. The signal would be very weak, Dr. Taylor points out, but not impossible of detection with the present refinement of receiving instruments, provided no great absorption took place in interstellar space. A high frequency wave will be used, as such a wave penetrates readily the earth's atmosphere and probably goes far beyond. The frequency of the wave will range between 20,000 and 30,000 kilocycles. Twenty kilowats of power will be used, enough to furnish current for about forty flatirons. The value of a radio signal to the moon lies in the confirmation of whether there is or not heavy absorption of waves in the upper levels of our own atmosphere. If successful it would indicate a reasonably good reflection coefficient at the surface of the moon--the power of the moon's surface to act as a joint agent in the perfection of the signal. The signal might have some bearing also on whether the moon has an atmosphere--something pretty much settled already by astronomical observation. It would also lead to the possibility of fairly accurate determination of wave velocity in free space, all of interest to science, either confirming existing theories or establishing new ones. The Pirate Planet PART TWO OF A FOUR-PART NOVEL _By Charles W. Diffin_ It is war. Interplanetary war. And on far distant Venus two fighting Earthlings stand up against a whole planet run amuck. WHAT HAS GONE BEFORE A flash of light on Venus!--and at Maricopa Flying Field Lieutenant McGuire and Captain Blake laugh at its possible meaning until the radio's weird call and the sight of a giant ship in the night sky prove their wildest thoughts are facts. "Big as an ocean liner," it hangs in midair, then turns and shoots upward at incredible speed until it disappears entirely, in space! McGuire goes to Mount Lawson observatory, and there he sees the flash on Venus repeated. Professor Sykes, who had observed the first flash, confirms it and sees still more. He sees the enveloping clouds of Venus torn asunder, and beneath them an identifying mark, a continent shaped like the letter "L." And then the great ship comes again. It hovers above the observatory and settles slowly down. [Illustration: "Hold them off as long as you can!"]