Then, several centuries ago--the exact time is uncertain, for no written records are kept on Mercury--came the Great Storms. Their cause was unknown--some widespread atmospheric disturbance. These storms temporarily parted the clouds in many places, allowing the direct rays of the sun to fall upon the planet's surface. The resulting temperature destroyed all life, withered all vegetation, with its scorching blast. The inhabitants of the Fire Country were killed by hundreds of thousands, their cities deserted, their land laid a desert waste. These storms, which it appears began suddenly, have returned periodically ever since, making the region practically uninhabitable. Its surviving races, pushed outward toward the more temperate zone, were living, at this time I am describing, in a much lower state of civilization than the people of the Light Country--a civilization of comparative savagery. In the Light Country they were held as slaves. This region--thus very aptly known as the Fire Country--embraces a circular area directly underneath the sun. So far as I could learn, it extended outward roughly to those points where--if it had been visible--the sun would have appeared some halfway between zenith and horizon. Lying outside the circle, in a larger, concentric ring, is the zone known as the Light Country. Entirely free from the equatorial storms, no direct rays of sunlight have ever penetrated its protecting cloud blanket. Here exists the highest state of civilization on the planet. Beyond the Light Country, in another concentric ring, lies the Twilight Country. It forms a belt about the planet, beginning roughly at those points at which the sun would appear only a short distance above the horizon, and extending back to where the sun would be below the horizon. In this region, as its name implies, there is never more than twilight. It is lightest at the borders of the Light Country, and fades into night at its other side. Still farther, beyond the twilight zone, lies the region of perpetual night and cold--the Dark Country. This area embraces the rest of the planet, comprising something less than half of its entire surface. Here is eternal night--a night of Stygian darkness, unlighted even by the stars, since the same atmosphere makes them invisible. The Dark Country, so far as it has been explored--which is very little--is a rocky waste and a sea of solid ice that never melts. Near the borders of the Twilight Country a few people like our Eskimos exist--savages with huge white faces, and great, staring eyes. There are a few fur-bearing animals and birds, but except for this fringe of life the Dark Country is thought to be uninhabited, its terrible cold making life in any form impossible.