“what’s the matter?” asked tom, with a smile, as he beheld ned’s amazement.

“i thought the bottom was dropping out of the machine!” gasped the financial manager of the swift concern.

“just a plate glass window in the floor,” tom explained, with a chuckle. “it enables us to take a look below without sticking our heads out of the windows and looking over the side. yes, that’s the old atlantic there,” and he pointed to the heaving, foam-tipped waves that were lazily surging far down beneath them.

the air monarch was now well up and moving eastward at fast speed. as the motors warmed up, peltok fed them more and more gasoline until they were approaching their maximum.

meanwhile brinkley and hartman were going about adjusting bearings, putting oil where it was needed, and doing general work. being a new machine, the air monarch needed more oil than a craft that had been run some time and whose bearings would have been worn to smoothness.

“well, we’re on our way,” remarked tom, as he moved about the cabin looking at the indicators, noting the speed, and having a general eye to the performance of his newest and pet craft. “we’re on our way, and in less than three weeks, if we have luck, we’ll be right back where we started.”

“do you think you can do it?” asked ned.

tom did not answer for a moment. then, with a serious look on his face, he said:

“it’s taking a big chance, ned. twenty days is a very short time to circle the world. i know we talk about aeroplanes that do two hundred and fifty miles an hour. and if one could keep that up for a hundred hours the trick would be pulled off in about four days. but no machine made can keep that speed up constantly. not enough gasoline or oil could be carried for a continuous flight of that kind. a man would have to come down several times to replenish.

“of course the hundred thousand dollar prize offer doesn’t specify that the world must be circled in twenty days. if it takes thirty days to do it, the one who gets under the wire first, having used up less time than any of the others, will win. but there’s dad’s bet of twenty thousand with mr. burch and mr. trace. that specifies twenty days.”

“evidently they don’t think you have much of a chance, tom,” said ned. “they didn’t even come to long island to see you start.”

“no, they weren’t there. and i guess they think they have dad’s money won. but though they couldn’t be there, they were sports enough to wish me good luck in a telegram. it came just before we took off. but i don’t really believe they think their money is in danger. i’m going to do my best, though, to win for dad’s sake and my own. that hundred thousand will come in very useful, ned.”

“i’ll say it will! you’ve been spending a lot lately, and you owe mr. jacks fifteen thousand.”

“we’ll pay him!” tom said with a determined air. “we’ll be on easy street if i can flash home a winner. and she’s running mighty sweet now,” he added, as he listened to the purr and hum of the motors and the throb of the propellers.

a look around them showed no other contesting aircraft in sight. but that did not mean none were racing them for the prize. the red arrow might be close by, hidden from them in the mist. below them were several motor boats and a steamer or two, and whether or not any of these were the craft trying for the prize tom swift did not know.

“do you think kilborn and his crowd will make any trouble for you?” asked ned when he and tom were sitting at ease, lulled by the speedy, even motion of their craft.

“i think they’ll try,” was the answer. “they’re desperate, for some reason or other. one is that they want to beat me, of course. another is that there has been for some time a trade rivalry between us. as you know, i’ve been making aeroplanes for a concern and kilborn and his crowd are trying to get the business away from me. if i win this international race it will be a big feather in my cap. the swift aeroplanes will get a big advertisement out of it.”

“i see,” murmured ned.

brinkley appeared in the doorway of the room where tom and ned were sitting. there was a grin on the face of the former tank man.

“what is it?” asked tom.

“come and get it!” answered the other.

“grub ready so soon?” asked ned, who recognized the cook’s method of summoning them to eat.

“grub is ready,” repeated brinkley.

“time went mighty fast,” tom said. “i forgot all about cooking or eating. we really didn’t settle on who was to be cook.”

“well, joe sort of wished it onto me,” went on brinkley, with another grin. “i had a hand in it when i was running a tank over on the other side,” he went on, “and if you want me to, i’ll keep at it.”

“i’ll tell you better after i eat this grub you say is ready,” laughed tom.

“that’s a fair proposition,” admitted brinkley. “well, anyhow, it’s ready. you two can eat and joe and i will take a shot at the grub later.”

“yes,” assented tom. “somebody’s got to run the ship.”

they went out to the little dining apartment, and appetizing odors greeted the noses of tom and ned. they sniffed hungrily and soon were doing full justice to the meal.

“you’re elected, brinkley!” cried tom when half way through the menu.

“second the motion!” echoed ned, who was also doing his full share with knife and fork.

cooking aboard the air monarch was done on a gasoline stove. since no hydrogen gas was carried, as is the case in most dirigibles and balloons that cannot get helium, there was no danger of any explosion from an open flame.

there was plenty of food on board, and tom planned to buy more whenever a landing was made. he knew he would have to land several times along the world-circling route to enable gasoline, oil and other supplies to be taken aboard.

the meal was nearly over and tom was calculating how far they had come and what speed they had made so far, while ned was debating with himself whether he could eat another slice of boiled ham, when there came a series of loud noises from the motor compartment back of the dining salon.

“what’s that?” cried tom starting up.

“one of the main bearings has burned out!” exclaimed hartman. “oil feed failed. the bearing’s red-hot!”

at the same moment the craft began to lose speed. ned felt her being forced down, for when it does not move fast enough to overcome the pull of gravity, an aeroplane must fall. slower and slower moved the air monarch, and lower and lower she sank toward the heaving surface of the atlantic.