down below, the aeronauts could see the crowd, led by the police, scurrying to and fro. many individuals beside the officers appeared to be holding weapons, and, from the puffs of smoke that spurted out, it was evident that more shots were being fired. but the bullets could do no harm, and the red cloud, under the force of the rapidly revolving propellers, was soon beyond the center of the city.

"well, if that isn't the limit!" cried tom. "they must have taken us for a german war balloon, about to drop explosives on them."

"bless my liver!" ejaculated mr. damon, "i believe you're right. eh, mr. sharp?"

the veteran balloonist took a careful look over the craft before replying. then he spoke:

"it couldn't be that," and he shook his head, as if puzzled. "they would know no foreign airship would try any trick like that. beside, if by some remote possibility they did imagine it, there would be soldiers shooting at us, instead of the police. as it was, the whole population seemed anxious to bring us down."

"and they nearly did," added mr. damon. "if they had shot a few holes in the gas bag where would we be?"

"right in the air," answered the balloonist. "it would take several volleys of bullets to damage our aluminum container. it is in sections and when one, or even five compartments, for that matter, are pierced, there is enough gas in the others to sustain us. so they could not have damaged us much, even if they had shot a lot of holes in us. even without the gas container we can keep afloat by constantly moving, for the planes will serve their purpose. of course they could damage us, and maybe put some of our machinery out of business, and that would be a serious thing. but what puzzles me is why they fired at us at all."

"it couldn't be out of pure mischief; could it?" asked the young inventor.

"hardly. if we were in a savage country i could understand the natives firing at some such object as this airship, but the people of that city must have known what our craft was. they probably have read something about it in the news papers, and to deliberately fire on us, with the chance of disabling us, seems worse than barbarous."

"well, we won't give 'em another opportunity," commented mr. damon.

"no, indeed, not this city, but who knows but what the example may spread? we may be fired at the next town we sail over."

"then steer clear of the towns," advised tom.

"impossible. we must pass over some, but i'd like to solve this mystery."

the day passed without further incident, though they did not go low enough down over any city to drop any messages. it was decided that it would not be safe.

"we'll take a chance at night," suggested tom, and that evening, approaching a good-sized town in the dusk, several of the weighted envelopes were dropped overboard. doubtless persons walking along the street, who were startled by hearing something fall with a "thud" at their feet, were much startled to look up and see, dimly, a great, ghostly shape moving in the air. but there was no shooting, and, eventually, some of the messages reached mr. swift, in shopton. but he could not answer them for the airship kept on the move.

the night was spent floating in the air, with the engine stopped, and the red cloud floating lazily this way and that as the gentle winds shifted, for it was calm. the "anchorage" if such it may be called, was above a sparsely settled part of the country, and if the lights of the airship were seen from below, the farmers doubtless took them for some new stars or, possibly, a comet.

"now then for a fast, straight run!" cried tom, after breakfast had been served, and the big motor, with its twenty cylinders, started. "we'll be able to make the turn to-day, and then make for home, won't we, mr. sharp?"

"well, we could do it, tom," was the answer, "but i like this mode of traveling so that i think i'll lengthen the voyage. instead of turning at atlanta, what do you say to making for key west, and then starting back? that will be something of a trip. the red cloud is behaving much better than i hoped she would."

"i'm willing to go further if mr. damon is."

"oh, bless my shoe strings, i'm game!" exclaimed the eccentric man. "i always did want to go to key west, anyhow."

the craft was speeding along at a fast clip, and dinner that day was served about three miles in the air. then, desiring to test the gliding abilities of the airship, it was sent down on a long slant, with the propellers stationary, the shifting planes and rudders alone guiding it.

as the craft fairly slid down out of the sky, like a sled on a bank of fleecy snow, tom, who was peering ahead, with his hand on the steering wheel, cried out "i say! it looks as if we were going to run into a thunder storm!"

"how's that?" inquired mr. sharp, poking his head from the motor compartment.

"he says there's a big storm ahead," repeated mr. damon, "and i guess he's right. i see a big bank of dark clouds, and there is a roaring in the air."

mr. sharp, who had been making some adjustments to the motor went forward to take a look. the red cloud was swiftly gliding downward on a slant, straight toward a dark mass of vapor, that seemed to be rolling first one way, and then another, while as mr. damon had said, there was a low rumbling proceeding from it.

"that doesn't seem to be a thunder storm," spoke the balloonist, with a puzzled air.

they all regarded the dark mass of vapor intently for a few seconds. tom had brought the airship to a more level keel, and it was now spinning along under its own momentum, like a flat piece of tin, scaled by some lead. but it was headed for the clouds, if such they were, though losing speed by degrees.

"i'll have to start the motor!" exclaimed mr. sharp. "we don't want to run into a storm, if we can help it, though i don't ever remember seeing a thunder disturbance like that."

"whew! it's getting warm," suddenly announced the youth, and he let go of the steering wheel for a moment, while he took off his coat.

"that's what it is," agreed mr. damon, who also divested himself of his garments. "bless my spark plug, but it's like a july day. no wonder there's a thunderstorm ahead."

then mr. sharp uttered a cry. "that's no storm!" he fairly shouted. "it's a big forest fire! that's smoke we see! we must get out of this. turn around tom, while i start the engine. we must rise above it!"

he fairly leaped for the motor, and tom and mr. damon could hear him turning the levers and wheels, ready to start. but before the explosions came something happened. there was a sound as of some great, siren whistle blowing, and then, with a howl of the on rushing air, the red cloud, the propellers of which hung motionless on their shafts, was fairly sucked forward toward the fire, as the current sucks a boat over a water fall.

"start the motor! start the motor, mr. sharp!" cried tom.

"i'm trying to, but something seems to be the matter."

"we're being drawn right over the fire!" yelled mr. damon. "it's getting hotter every minute! can't you do something?"

"you take the wheel," called the balloonist to mr. damon. "steer around, just as if it was an auto when we start the engine. tom, come here and give me a hand. the motor has jammed!"

the young inventor sprang to obey. mr. damon, his face showing some of the fear he felt, grasped the steering wheel. the airship was now about a quarter of a mile high, but instead of resting motionless in the air, sustained by the gas in the container, she was being pulled forward, right toward the heart of the mass of black vapor, which it could now be seen was streaked with bright tongues of flame.

"what's making us go ahead, if the motor isn't going?" asked tom, as he bent over the machine, at which the aeronaut was laboring.

"suction—draught from the fire!" explained mr. sharp. "heated air rises and leaves a vacuum. the cold air rushes in. it's carrying us with it. we'll be right in the fire in a few minutes, if we can't get started with this motor! i don't see what ails it."

"can't we steer to one side, as it is?"

"no. we're right in a powerful current of air, and steering won't do any good, until we have some motion of our own. turn the gasolene lever on a little more, and see if you can get a spark."

tom did so, but no explosion resulted. the twenty cylinders of the big engine remained mute. the airship, meanwhile, was gathering speed, sucked onward and downward as it was by the draught from the fire. the roaring was plainer now, and the crackling of the flames could be heard plainly. the heat, too, grew more intense.

frantically tom and mr. sharp labored over the motor. with the perverseness usual to gas engines, it had refused to work at a critical moment.

"what shall i do?" cried mr. damon from his position in the pilot house. "we seem to be heading right for the midst of it?"

"slant the elevation rudder," called tom. "send the ship up. it will be cooler the higher we go. maybe we can float over it!"

"you'd better go out there," advised mr. sharp. "i'll keep at this motor. go up as high as you can. turn on more gas. that will elevate us, but maybe not quick enough. the gas doesn't generate well in great heat. i'm afraid we're in for it," he added grimly.

tom sprang to relieve mr. damon. the heat was now intense. nearer and nearer came the red cloud to the blazing forest, which seemed to cover several square miles. great masses of smoke, with huge pieces of charred and blazing wood carried up by the great draught, circled around the ship. the red cloud was being pulled into the midst of the fire by the strong suction. tom yanked over the elevation rudder, and the nose of the craft pointed upward. but it still moved downward, and, a moment later the travelers of the air felt as if they were over a fiery furnace.