"When I had read how they went into action and what they accomplished against the barbed wire entanglements, and how they crossed the trenches, I concluded that a bigger tank, one capable of more speed, say ten or twelve miles an hour, and one that could cross bigger excavations--the English tanks up to this time can cross a ditch of twelve feet--I thought that, with one made on such specifications, more effective work could be done against the Germans." "And will yours do that?" asked Ned. "I mean will it do ten miles an hour, and straddle over a wider ditch than twelve feet?" "It'll do both," promptly answered Tom. "We did a little better than eleven miles an hour a while ago when I yelled to you to get out of the way just now. It's true we weren't under good control, but the speed had nothing to do with that. And as for going over a big ditch, I think we straddled one about fourteen feet across back there, and we can do better when I get my grippers to working." "Grippers!" exclaimed Mary. "What kind of trench slang is that, Tom Swift?" asked Mr. Damon. "Well, that's a new idea I'm going to try out It's something like this," and while from a distant part of the interior of Tank A came the sound of hammering, the young inventor rapidly drew a rough pencil sketch. It showed the tank in outline, much as appear the pictures of tanks already in service--the former simile of two wedge-shaped pieces of metal put together broad end to broad end, still holding good. From one end of the tank, as Tom drew it, there extended two long arms of latticed steel construction. "The idea is," said Tom, "to lay these down in front of the tank, by means of cams and levers operated from inside. If we get to a ditch which we can't climb down into and out again, or bridge with the belt caterpillar wheels, we'll use the grippers. They'll be laid down, taking a grip on the far side of the trench, and we'll slide across on them." "And leave them there?" asked Mr. Damon. "No, we won't leave them. We'll pick them up after we have passed over them and use them in front again as we need them. A couple of extra pairs of grippers may be carried for emergencies, but I plan to use the same ones over and over again." "But what makes it go?" asked Mary. "I don't want all the details, Tom," she said, with a smile, "but I'd like to know what makes your tank move." "I'll be able to show you in a little while," he answered. "But it may be enough now if I tell you that the main power consists of two big gasolene engines, one on either side. They can be geared to operate together or separately. And these engines turn the endless belts made of broad, steel plates, on which the tank travels. The belts pass along the outer edges of the tank longitudinally, and go around cogged wheels at either end of the blunt noses.