Chapter XIII
Into a Trench
Tom cast a hasty glance over the mechanism of the machine before hestarted to cross the stream by the additional aid of the grippers, orspanners, as he sometimes called this latest device.
Along each side, in a row of sockets, were two long girders of steel,latticed like the main supports of a bridge. They were of peculiartriangular construction, designed to support heavy weights, and eachend was broadly flanged to prevent its sinking too deeply into theearth on either side of a gully or a stream.
The grippers also had a sort of clawlike arrangement on either end,working on the principle of an "orange-peel" shovel, and these clawswere designed to grip the earth to prevent slipping.
The spanners would be pulled out from their sockets on the side of thetank by means of steel cables, which were operated from within. Theywould be run out across the gap and fastened in place. The tank wasdesigned to travel along them to the other side of the gap, and, oncethere, to pick up the girders, slip them back into place on the sides,and the engine of war would travel on.
"You are mightily excited, Tom.
"I admit it, Ned. You see, I have not tried the grippers out except ona small model. They worked there, but whether they will work inpractice remains to be seen. Of course, at this stage, I'm willing tostake my all on the results, but there is always a half-question untilthe final try-out under practical conditions."
"Well, we'll soon see," said one of the workmen. "Are you ready, Mr.Swift?"
"All ready," answered Tom.
Tank A, as she was officially known, had come to a stop, as has beensaid, on the very edge of Tinkle Creek. The banks were fairly solidhere, and descended precipitously to the water ten feet below. Theshores were about twenty feet apart.
"Suppose the spanners break when you're halfway over, Tom?" asked hischum.
"I don't like to suppose anything of the sort. But if they do, we'regoing down!"
"Can you get up again?"
"That remains to be seen," was the non-committal reply. "Well, heregoes, anyhow!"
Going up into the observation tower, which was only slightly raisedabove the roof of the highest part of the tank, Tom gave the signal forthe motors to start. There was a trembling throughout the whole of thevast structure. Tom threw back a lever and Ned, peering from a sideobservation slot, beheld a strange sight.
Like the main arm of some great steam shovel, two long, latticedgirders of steel shot out from the sides of the tank. They gave a halfturn, as they were pulled forward by the steel ropes, so that they laywith their broader surfaces uppermost.
Straight across the stream they were pulled, their clawlike ends comingto a rest on the opposite bank. Then they were tightened into place bya backward pull on the operating cables, and Tom, with a sigh ofrelief, announced:
"Well, so far so good!"
"Do we go over now?" inquired Ned.
"Over the top--yes, I hope," answered Tom, with a laugh. "How aboutyou down there?" he called to the engine room through a telephone whichcould only be used when the machinery was not in action, there beingtoo much noise to permit the use of any but visual signals after that.
"All right," came back the answer. "We're ready when you are."
"Then here we go!" said Tom. "Hold fast, Ned! Of course there's no realtelling what will happen, though I believe we'll come out of it alive."
"Cheerful prospect," murmured Ned.
The grippers were now in place. It only remained for the tank to propelherself over them, pick them up on the other side of Tinkle Creek, andproceed on her course.
Tom Swift hesitated a moment, one hand on the starting lever and theother on the steering wheel. Then, with a glance at Ned, half whimsicaland half resolute, Tom started Tank A on what might prove to be herlast journey.
Slowly the ponderous caterpillar belts moved around on the sprocketwheels. They ground with a clash of steel on the surface of thespanners. So long was the tank that the forward end, or the "nose," washalfway across the stream before the bottom part of the endless beltsgripped the latticed bridge.
"If we fall, we'll span the creek, not fall into it," murmured Ned, ashe looked from the observation slot.
"That's what I counted on," Tom said. "We'll get out, even if we dofall."
But Tank A was not destined to fall. In another moment her entireweight rested on the novel and transportable bridge Tom Swift hadevolved. Then, as the gripping ends of the girders sank farther intothe soil, the tank went on her way.
Slowly, at half speed, she crawled over the steel beams, makingprogress over the creek and as safely above the water as though on aregularly constructed bridge.
On and on she went. Now her entire weight was over the middle of thetemporary structures. If they were going to give way at all, it wouldbe at this point. But they did not give. The latticed and triangularsteel, than which there is no stronger form of construction, held upthe immense weight of Tank A, and on this novel bridge she propelledherself across Tinkle Creek.
"Well, the worst is over," remarked Ned, as he saw the nose of the tankproject beyond the farthermost bank.
"Yes, even if they collapse now nothing much can happen," Tom answered."It won't be any worse than wallowing down into a trench and out again.But I think the spanners will hold."
And hold they did! They held, giving way not a fraction of an inch,until the tank was safely across, and then, after a little delay, dueto a jamming of one of the recovery cables, the spanners were pickedup, slid into the receiving sockets, and the great war engine was readyto proceed again.
"Hurrah!" cried Ned. "She did it, Tom, old man!" and he clapped hischum resoundingly on the back.
"She certainly did!" was the answer. "But you needn't knock me aparttelling me that. Go easy!"
"Bless my apple pie!" cried Mr. Damon, who was as much pleased aseither of the boys, "this is what I call great!"
"Yes, she did all that I could have hoped for," said Tom. "Now for thenext test."
"Bless my collar button! is there another?"
"Just down into a trench and out again." Tom said. "This iscomparatively simple. It's only what she'll have to do every day inFlanders."
The tank waddled on. A duck's sidewise walk is about the only kind ofmotion that can be compared to it. The going was easier now, for it wasacross a big field, and Tom told his friends that at the other end wasa deep, steep and rocky ravine in which he had decided to give the tankanother test.
"We'll imagine that ravine is a trench," he said, "and that we've gotto get on the other side of it. Of course, we won't be under fire, asthe tanks will be at the front, but aside from that the test will bejust as severe."
A little later Tank A brought her occupants to the edge of the "trench."
"Now, little girl," cried Tom exultingly, patting the rough steel sideof his tank, "show them what you can do!"
"Bless my plum pudding!" cried Mr. Damon, "are you really going downthere, Tom Swift?"
"I am," answered the young inventor. "It won't be dangerous. We'llcrawl down and crawl out. Hold fast!"
He steered the machine straight for the edge of the ravine, and as thenose slipped over and the broad steel belts bit into the earth the tanktilted downward at a sickening angle.
She appeared to be making the descent safely, when there was a suddenchange. The earth seemed to slip out from under the broad caterpillarbelts, and then the tank moved more rapidly.
"Tom, we're turning over!" shouted Ned. "We're capsizing!"