there was little time to lose. every moment of delay meant so much less chance for the recovery of mr. swift. even now the periods of consciousness were becoming shorter and farther apart. he seemed to be sinking.

tom resolutely refused to think of the possibility of death, as he went in to bid his parent good-by before starting off on his trip through the air. mr. swift barely knew his son, and, with tears in his eyes, though he bravely tried to keep them back, the young inventor went out into the yard.

there stood the humming-bird, with mr. jackson, mr. damon and eradicate working over her, to get her in perfect trim for the race before her—a race with death.

fortunately there was little to be done to get the speedy craft ready. tom had accomplished most of what was necessary, while waiting for word from dr. hendrix. now about all that needed to be done was to see that there was plenty of gasoline and oil in the reservoirs.

"i'll give you a note to dr. hendrix," said mr. gladby, as tom was fastening on his faceguard. "i—i trust you won't be disappointed, tom. i hope he will consent to return with you."

"he's got to come," said the young inventor, simply, as if that was all there was to it.

"do you think you can make the trip in time?" asked mr. damon. "it is a little less than a hundred miles in an airline, but you have to go and go back. can the aeroplane do it?"

"i'd be ashamed of her if she couldn't," said tom, with a grim tightening of his lips. "she's just got to do it; that's all! but i know she will," and he patted the big propeller and the motor's shining cylinders as though the machine was a thing alive, like a horse or a dog, who could understand him.

he climbed to his seat, the other one holding a bag of sand to maintain a good balance.

"start her," ordered tom, and mr. jackson twisted the propeller. the motor caught at once, and the air throbbed with the noise of the explosions. tom listened to the tune of the machinery. it sang true.

"two thousand pounds thrust!" called the engineer, as he looked at the scale.

"let her go!" cried tom, whose voice was hardly heard above the roar. the trim little aeroplane scudded over the ground, gathering speed at every revolution of the wheels. then with a spring like that of some great bird launching itself in flight, she left the earth, and took to the air. tom was off on his trip.

those left behind sent up a cautious cheer, for they did not want to disturb mr. swift. they waved their hands to the young inventor, and he waved his in reply. then he settled down for one of the swiftest flights he had ever undertaken.

tom ascended until he struck a favorable current of air. there was a little wind blowing in the direction he wished to take, and that aided him. but even against a powerful head-wind the humming-bird could make progress.

the young inventor saw the ground slipping backward beneath him. carefully he watched the various indicators, and listened intently to the sound of the cylinders' explosions. they came rapidly and regularly. the motor was working well.

tom glanced at the barograph. it registered two thousand feet, and he decided to keep at about that height, as it gave him a good view, and he could see to steer, for a route had been hastily mapped out for him by his friends.

over cities, towns, villages, scattered farmhouses; across stretches of forest; over rivers, above big stretches of open country he flew. often he could see eager crowds below, gazing up at him. but he paid no heed. he was looking for a sight of a certain broad river, which was near kirkville. then he knew he would be close to his goal.

he had speeded up the motor to the limit, and there was nothing to do now, save to manage the planes, wing tips and rudders, and to see that the gasoline and oil were properly fed to the machine.

faster and faster went the humming-bird, but tom's thoughts were even faster. he was thinking of many things—of his father—of what he would do if mr. swift died—of the mysterious airship—of the stolen plans—of the fire in the shed—of the great race—and of andy foger.

he took little note of time, and when, in less than an hour he sighted the river that told him he was near to kirkville, he was rather startled.

"you certainly did come right along, humming-bird!" he murmured proudly.

he descended several hundred feet, and, as he passed over the town, the people of which grew wildly excited, he looked about for the house of the noted specialist. he knew how to pick it out, for dr. gladby had described it to him, and tom was glad to see, as he came within view of the residence, that it was surrounded by a large yard.

"i can land almost at his door," he said, and he did, volplaning to earth with an ease born of long practice.

to say that dr. hendrix was astonished when tom dropped in on him in this manner, would not be exactly true. the specialist was not in the habit of receiving calls from youths in aeroplanes, but the fact was, that dr. hendrix was so absorbed in his work, and thought so constantly about it, that it took a great deal to startle him out of his usual calm.

"and so you came for me in your aeroplane?" he asked of tom, as he gazed at the trim little craft. it is doubtful if he really saw it, however, as dr. hendrix was just then thinking of an operation he had performed a few hours before. "i'm sorry you had your trip for nothing," he went on. "i'd like very much to come to your father, but didn't you get my telegram, telling about the broken bridge? there is no way for me to get to shopton in time."

"yes, there is!" cried tom, eagerly.

"how?"

"the same way i came—in the aeroplane! dr. hendrix you must go back with me! it's the only way to save my father's life. come with me in the humming-bird. it's perfectly safe. i can make the trip in less than an hour. i can carry you and your instruments. will you come? won't you come to save my father's life?" tom was fairly pleading now.

"a trip in an aeroplane," mused dr. hendrix "i've never taken such a thing. i—"

"don't be afraid, there's really no danger," said tom.

the physician seemed to reach a sudden conclusion. his eyes brightened. he walked over and looked at the little humming-bird. for the time being he forgot about his operations.

"i'll go with you!" he suddenly cried. "i'll go with you, tom swift! if you've got the nerve, so have i! and if my science and skill can save your father's life, he'll live to be an old man! wait until i get my bag and i'll be with you!"

tom's heart gave a bound of hope.