"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.