Only too true were the words Ned Newton shouted to his chum. Tank A was really capsizing. She had advanced to the edge of the gully and started down it, moving slowly on the caterpillar bands of steel. Then had come a sudden lurch, caused, as they learned afterward, by the slipping off of a great quantity of shale from an underlying shelf of rock.

This made unstable footing for the tank. One side sank lower than the other, and before Tom could neutralize this by speeding up one motor and slowing down the other the tank slowly turned over on its side.

"But she isn't going to stop here!" cried Ned, as he found himself thrown about like a pill in a box. "We're going all the way over!"

"Let her go over!" cried Tom, not that he could stop the tank now. "It won't hurt her. She's built for lust this sort of thing!"

And over Tank A did go. Over and over she rolled, sidewise, tumbling and sliding down the shale sides of the great gully.

"Hold fast! Grab the rings!" cried Tom to his two companions in the tower with him. "That's what they're for!"

Ned and Mr. Damon understood. In fact, the latter had already done as Tom suggested. The young inventor had read that the British tanks frequently turned turtle, and he had this in mind when he made provision in his own for the safety of passengers and crew.

As soon as he felt the tank careening, Tom had pressed the signal ordering the motors stopped, and now only the force of gravity was operating. But that was sufficient to carry the big machine to the bottom of the gulch, whither she slid with a great cloud of sand, shale and dust.

"Bless my--bless my--" Mn Damon was murmuring, but he was so flopped about, tossed from one side to the other, and it took so much of his attention and strength to hold on to the safety ring, that he could not properly give vent; to one of his favorite expressions.

But there comes an end to all things, even to the descent of a tank, and Tom's big machine soon stopped rolling, sliding, and turning improvised somersaults, and rested in a pile of soft shale at the bottom of the gully. And the tank was resting on her back!

"We've turned turtle!" cried Ned, as he noted that he was standing on what, before, had been the ceiling of the observation tower. But as everything was of steel, and as there was no movable furniture, no great harm was done. In fact, one could as well walk on the ceiling of the tank as on the floor.

"But how are you going to get her right side up?" asked Mr. Damon.

"Oh, turning upside down is only one of the stunts of the game. I can right her," was the answer.

"How?" asked Ned.

"Well, she'll right herself if there's ground enough for the steel belts to get a grip on.

"But can the motors work upside down?"

"They surely can!" responded Tom. "I made 'em that way on purpose. The gasolene feeds by air pressure, and that works standing on its head, as well as any other way. It's going to be a bit awkward for the men to operate the controls, but we won't be this way long. Before I start to right her. though, I want to make sure nothing is broken."

Tom signaled to the engine room, and, as the power was off and the speaking tube could be used, he called through it:

"How are you down there?"

"Right-o!" came back the answer from a little Englishman Tom had hired because he knew something about the British tanks. "'Twas a bit of nastiness for a while, but it won't take us long to get up ag'in."

"That's good!" commented Tom. "I'll come down and have a look at you."

It was no easy matter, with the tank capsized, to get to the main engine room, but Tom Swift managed it. To his delight, aside from a small break in one of the minor machines, which would not interfere with the operation or motive force of the monster war engine, everything was in good shape. There was no leak from the gasolene tanks, which was one of the contingencies Tom feared, and, as he had said, the motors would work upside down as well as right side up, a fact he had proved more than once in his Hawk.

"Well, we'll make a start," he told his chief engineer. "Stand by when I give the signal, and we'll try to crawl out of this right side up."

"How are you going to do it?" asked Ned, as his chum crawled back into the observation tower.

"Well, I'm going to run her part way up the very steepest part of the ravine I can find--the side of a house would do as well if it could stand the strain. I'm going to stand the tank right up on her nose, so to speak, and tip her over so she'll come right again."

Slowly the tank started off, while Tom and his friends in the observation tower anxiously awaited the result of the novel progress. Ned and Mr. Damon clung to the safety rings. Tom put his arm through one and hung on grimly, while he used both hands on the steering apparatus and the controls.

Of course the trailer wheels were useless in a case of this kind, and the tank had to be guided by the two belts run at varying speeds.

"Here we go!" cried Tom, and the tank started. It was a queer sensation to be moving upside down, but it did not last very long. Tom steered the tank straight at the opposite wail of the ravine, where it rose steeply. One of the broad belts ran up on that side. The other was revolved in the opposite direction. Up and up, at a sickening angle, went Tank A.

Slowly the tank careened, turning completely over on her longer axis, until, as Tom shut off the power, he and his friends once more found themselves standing where they belonged--on the floor of the observation tower.

"Right side up with care!" quoted Ned, with a laugh. "Well, that was some stunt--believe me!"

"Bless my corn plaster, I should say so!" cried Mr. Damon.

"Well, I'm glad it happened," commented Tom. "It showed what she can do when she's put to it. Now we'll get out of this ditch."

Slowly the tank lumbered along, proper side up now, the men in the motor room reporting that everything was all right, and that with the exception of a slight unimportant break, no damage had been done.

Straight for the opposite steep side of the gully Tom directed his strange craft, and at a point where the wall of the gulch gave a good footing for the steel belts, Tank A pulled herself out and up to level ground.

"Well, I'm glad that's over," remarked Ned, with a sigh of relief, as the tank waddled along a straight stretch. "And to think of having to do that same thing under heavy fire !"

"That's part of the game," remarked Tom. "And don't forget that we can fire, too--or we'll be able to when I get the guns in place. They'll help to balance the machine better, too, and render her less likely to overturn."

Tom considered the test a satisfactory one and, a little later, guided his tank back to the shop, where men were set to work repairing the little damage done and making some adjustments.

"What's next on the program?" asked Ned of his chum one day about a week later. "Any more tests in view?"

"Yes," answered Tom. "I've got the machine guns in place now. We are going to try them out and also endeavor to demolish a building and some barbed wire. Like to come along?"

"I would!" cried Ned.

A little later the tank was making her way over a field. Tom pointed toward a deserted factory, which had long been partly in ruins, but some of the walls of which still stood.

"I'm going to bombard that," he announced, and then try to batter it down and roll over it like a Juggernaut. Are you game?"

"Do your worst!" laughed Ned. "Let me man one of the machine guns!"

"All right," agreed Tom. "Concentrate your fire. Make believe you're going against the Germans!"

Slowly, but with resistless energy, the tank approached the ruined factory.

"Are you sure there's no one in it, Tom?"

"Sure! Blaze away!"