Ned Newton sighted his machine gun. Tom had showed him how to work it, and indeed the young bank clerk had had some practice with a weapon like this, erected on a stationary tripod. But this was the first time Ned had attempted to fire from the tank while it was moving, and he found it an altogether different matter.

"Say, it sure is hard to aim where you want to!" he shouted across to Tom, it being necessary, even in the conning tower, where this one gun was mounted, to speak loudly to make one's self heard above the hum, the roar and rattle of the machinery in the interior of Tank A, and below and to the rear of the two young men.

"Well, that's part of the game," Tom answered. "I'm sending her along over as smooth ground as I can pick out, but it's rough at best. Still this is nothing to what you'll get in Flanders."

"If I get there!" exclaimed Ned grimly. "Well, here goes!" and once more he tried to aim the machine gun at the middle of the brick wall of the ruined factory.

A moment later there was a rattle and a roar as the quick- firing mechanism started, and a veritable hail of bullets swept out at the masonry. Tom and Ned could see where they struck, knocking off bits of stone, brick and cement

"Sweep it, Ned! Sweep it!" cried Tom. "Imagine a crowd of Germans are charging out at you, and sweep 'em out of the way!"

Obeying this command, the young man moved the barrel of the machine gun from side to side and slightly up and down. The effect was at once apparent. The wall showed spatter- marks of the bullets over a wider area, and had a body of Teutons been before the factory, or even inside it, many of them would have been accounted for, since there were several holes in the wall through which Ned's bullets sped, carrying potential death with them.

"That's better!" shouted Tom. "That'll do the business! Now I'm going to open her up, Ned!"

"Open her up?" cried the young bank clerk, as he ceased firing.

"Yes; crack the wall of that factory as I would a nut! Watch me take it on high--that is, if the old tank doesn't go back on me!"

"You mean you're going to ride right over that building, Tom ?"

"I mean I'm going to try! If Tank A does as I expect her to, she'll butt into that wall, crush it down by force and weight, and then waddle over the ruins. Watch!"

Tom sent some signals to the motor room. At once there was noticed an increase in the vibrations of the ponderous machine.

"They're giving her more speed," said Tom. "And I guess we'll need it."

Straight for the old factory went Tank A. In spite of its ruined condition, some of the walls were still firm, and seemed to offer a big obstacle to even so powerful an engine of war as this monstrous tank.

"Get ready now, Ned," Tom advised. "And when I crack her open for you cut loose with the machine gun again. This gun is supposed to fire straight ahead and a little to either side. There are other guns at left and right, amidships, as I might say, and there's also one in the stern, to take care of any attack from that direction.

"The men in charge of them will fire at the same time you do, and it will be as near like a real attack as we can make it--with the exception of not being fired back at. And I wouldn't mind if such were the case, for I don't believe anything, outside of heavy artillery, will have any effect on this tank."

Tank A was now almost at her maximum speed as she approached closer to the deserted factory. Ned and Tom, in the conning tower, saw the largest of the remaining walls looming before them. Straight at it rushed the ponderous machine, and the next moment there came a shock which almost threw Ned away from his gun and back against the steel wall behind him.

"Hold fast!" cried Tom. "Here we go! Fire. Ned! Fire!"

There was a crash as the blunt nose of the great war tank hit the wall and crumpled it up.

A great hole was made in the masonry, and what was not crushed under the caterpillar belts of the tank fell in a shower of bricks, stone and cement on top of the machine.

Like a great hail storm the broken masonry pelted the steel sides and top of the tank. But she felt them no more than does an alligator the attacks of a colony of ants. Right on through the dust the tank crushed her way. Added to the noise of the falling walls was that of the machine guns, which were barking away like a kennel of angry hounds eager to be unleashed at the quarry.

Ned kept his gun going until the heat of it warned him to stop and let the barrel cool, or he knew he would jam some of the mechanism. The other guns were firing, too, and the bullets sent up little spatter points of dust as they hit.

"Great jumping hoptoads!" yelled Ned above the riot of racket outside and inside. "Feel her go, Tom!"

"Yes, she's just chewing it up, all right!" cried the young inventor, his eyes shining with delight.

The tank had actually burst her way through the solid wall of the old factory, permission to complete the demolition of which Tom had secured from the owners. Then the great machine kept right on. She fairly "walked" over the piles of masonry, dipped down into what had been a basement, now partly filled with debris, and kept on toward another wall.

"I'm going through that, too!" cried Tom.

And he did, knocking it down and sending his tank over the piled-up ruins, while the machine guns barked, coughed and spluttered, as Ned and the others inside the tank held back the firing levers.

Right through the opposite wall, as through the one she had already demolished, the tank careened on her way, to emerge, rather battered and dust-covered, on the other side of what was left of the factory. And there was not much of it left. Tank A had well-nigh completed its demolition.

"If there'd been a nest of Germans in there," said Tom, as he brought the machine to a stop in a field beyond the factory, "they'd have gotten out in a hurry."

"Or taken the consequences," added Ned, as he wiped the sweat from his powder-blackened and oil-smeared face. "I certainly kept my gun going."

"Yes, and so did the others," reported one of the mechanics, as he emerged from the "cubby hole," where the great motors had now ceased their hum and roar.

"How'd she stand it?" asked Tom.

"All right inside," answered the man. "I was wondering how she looks from the outside."

"Oh, it would take more than that to damage her," said Tom, with pardonable pride. "That was pie for her! Solid concrete, which she may have to chew up on the Western front, may present another kind of problem, but I guess she'll be able to master that too. Well, let's have a look."

He and Ned, with some of the crew and gunners, went outside the tank. She was a sorry-looking sight, very different from the trim appearance she had presented when she first left the shop. Bricks, bits of stone, and piles of broken cement in chunks and dust lay thick on her broad back. But no real damage had been done, as a hasty examination showed.

"Well, are you satisfied, Tom?" asked his chum.

"Yes, and more," was the answer. "Of course this wasn't the hardest test to which she could have been submitted, but it will do to show what punishment she can stand. Being shot at from big guns is another matter. I'll have to wait until she gets to Flanders to see what effect that will have. But I know the kind of armor skin she has, and that doesn't worry me. There's one thing more I want to do while I have her out now."

"What's that?" asked Ned.

"Take her for a long trip cross country, and then shove her through some extra heavy barbed wire. I'm certain she'll chew that up, but I want to see it actually done. So now, if you want to come along, Ned, we'll go cross country."

"I'm with you!"

"Get inside then. We'll let the dust and masonry blow and rattle off as we go along."

The tank started off across the fields, which stretched for many miles on either side of the deserted factory, when suddenly Ned, who was again at his post in the observation tower, called:

"Look, Tom!"

"What at?"

"That corner of the factory which is still standing. Look at those men coming out and running away!"

Ned pointed, and his chum, leaning over from the steering wheel and controls, gave a start of surprise as he saw three figures clambering down over the broken debris and making their way out of what had once been a doorway.

"Did they come out of the factory, Ned?"

"They surely did! And unless I miss my guess they were in it, or around it, when we went through like a fellow carrying the football over the line for a touchdown."

"In there when the tank broke open things?"

"I think so. I didn't see them before, but they certainly ran out as we started away."

"This has got to be looked into!" decided Tom. "Come on, Ned! It may be more of that spy business !"

Tom Swift stopped the tank and prepared to get out