So much, in general, for the main geographical features of Mercury. The Great City stands about halfway between the borders of the Fire Country and the edge of the twilight zone. This level marshland, the barren, metallic mountains, and a sort of semitropic jungle, partly inundated by water, comprise nearly all the area of the Light Country. From the Great City, through the watery jungle, extends a system of little winding bayous--a perfect maze of them, with hundreds of intercommunicating branches--which it would be almost impossible to traverse without losing all sense of direction. Beyond these bayous, into which their sluggish currents flow, lies the Narrow Sea. On its farther shore begins the Twilight Country, much of it a barren, semifrigid waste, with a little level, tillable land, vast rocky mountain ranges, and a few forests. In spite of its inhospitable character the Twilight Country is fairly densely populated; and, I realized when I got into it, civilized life is exceedingly difficult to maintain there. I understood then why the Twilight People were so envious of land in the Light Country; and, in truth, I could not blame them for that, or for looking toward our earth with longing. But just as the Light Country People had defended their borders with implacable determination, so was I determined that they should not invade my world, either. And I was ready to stake my life and even the lives of those I loved here on Mercury in the attempt to prevent them. CHAPTER XVII. THE FIGHT AT THE BAYOU. Miela proceeded to explain our plan in detail to these fifteen hundred enthusiastic allies. It was my idea to build several platforms similar to this one on which Mercer and I had been carried up here into the mountains, only somewhat larger. We then proposed to seize these emissaries of Tao--there were not more than eight or ten of them altogether in the Great City--capturing them at night, without alarm, if possible, and transporting them summarily into the Twilight Country. My theory was that if they were to disappear thus mysteriously the people of the Great City would have no particular cause to make trouble afterward, and we hoped that the affair would soon be forgotten. Miela thought it practical for us to carry them in this way across the Narrow Sea. The Lone City, from which Tao was operating, was located near the edge of the sea, and if we gave them food they would be enabled to reach it in safety in a day or two. The girls agreed enthusiastically with this plan, and we selected a number to carry it out. Meanwhile we planned also to organize a system of aërial patrols, and detailed some two hundred of the girls, who in varying shifts were to fly back and forth along the borders of the sea over its Light Country shore, to make sure that Tao did not attempt to make a crossing by water. "Can't they fly over as well as we can?" Mercer objected. "Their women fly, too, don't they?"