of these ships, invisible to the inhabitants of Barsoom. Perhaps two million of them will invade Helium and overrun her two principal cities before a single inhabitant is aware that a single enemy threatens their security. They will come with lethal weapons of which Barsoomians know nothing and which they cannot, therefore, combat."

"Invisible ships!" I exclaimed. "Why I saw this one plainly after I was captured."

"Yes," he said. "It was not invisible then, but it was invisible when it came in broad daylight under the bows of your patrol ships and landed in one of the most prominent places in all Lesser Helium. It was not invisible when you first saw it; because it had cast off its invisibility, or, rather, the Morgors had cast it off so that they might find it again themselves, for otherwise it would have been as invisible to them as to us."

"Do you know how they achieve this invisibility?" I asked.

"Multis Par has explained it to me," relied U Dan. "Let me see; I am not much of a scientist, but I think that I recall more or less correctly what he told me. It seems that on some of the ocean beaches on Sasoom there is a submicroscopic, magnetic sand composed of prismatic crystals. When the Morgors desire invisibility for a ship, they magnetize the hull; and then, from countless tiny apertures in the hull, they coat the whole exterior of the ship with these prismatic crystals. They simply spray them out, and they settle in a cloud upon the hull, causing light rays to bend around the ship. The instant that the hull is demagnetized, these tiny particles, light as air, fall or are blown off; and instantly the ship is visible again."

<<BackPagesTo menuNext>>