A thick haze hung over the dark landscape, which was just visible in the dim starlight. A tense quiet prevailed. The _Sphere’s_ stall was readied quickly. All was well, and a few minutes later Robert and Taggert were rising rapidly in it above the sleeping city. The package given Robert by Zola was discovered to contain a small bottle of excellent wine and some _lana_, a nutritious cake, both of which were quite welcome, as he had not eaten anything for several hours. Rising to a height of about four thousand feet, Robert allowed the _Sphere_ to drift slowly over the enemy’s lines. With the ports open, the sound of activity below came to them with startling clearness. It was plain that preparations were being made for an attack on the city. Robert had reduced the speed of the gyrostats to a minimum in order that the invaders might not be aware of its proximity. Every light in the _Sphere_ was extinguished. It hung above the busy Martians--a great, dark globe of unsuspected menace. Suddenly a sharp command rang out below. Immediately there followed a series of flashes accompanied by a corresponding series of dull thuds--sounds of the curious Martian electric artillery in action. Robert’s heart sank as he thought of Zola’s danger. With the first thuds of the artillery below and the answering fire from the metropolis, the entire plain seemed fairly to seethe with activity. Bugles were blown, and commands rang out above the other sounds. Robert switched on the _Sphere’s_ giant searchlight. A blinding shaft of light shot down upon the broiling mass of humanity beneath. A great cry of consternation was wafted up to them. “Not exactly elated at our presence,” remarked Taggert, dryly. “We’ll be about as welcome as a plague a few minutes from now,” remarked Robert. Swinging the reflector about, he followed every movement of the army of invaders, pausing at intervals to flash instructions to the defenders by a prearranged code of signals corresponding to the smoke signals of the day. Already the enemy was swarming upon the small force of defenders in the outskirts of the metropolis. Several projectiles sang past the _Sphere_, indicating that the invaders were not going to submit to its presence idly. A number of smaller searchlights were directed upon it from beneath, almost blinding Robert and Taggert as their eyes sought to pierce the darkness below. The invaders were not without defense. Adopting a swift, staggered course, Robert managed partly to avoid the blinding beams of light. Instructing Taggert to continue these tactics, Robert prepared to use the _Sphere’s_ powerful weapon, the Norrensen Tube, against their enemies. He prayed only that it would not fail him now, and that their power would hold out long enough.