t selected for the test the
banks were high and steep.

"If she bridges that gap she'll do anything," murmured Ned, as the tank
came to a stop on the edge.

Chapter XIII

Into a Trench

Tom cast a hasty glance over the mechanism of the machine before he
started to cross the stream by the additional aid of the grippers, or
spanners, 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 peculiar
triangular construction, designed to support heavy weights, and each
end was broadly flanged to prevent its sinking too deeply into the
earth 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 claws
were designed to grip the earth to prevent slipping.

The spanners would be pulled out from their sockets on the side of the
tank by means of steel cables, which were operated from within. They
would be run out across the gap and fastened in place. The tank was
designed to travel along them to the other side of the gap, and, once
there, to pick tip 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 on
a small model. They worked there, but whether they will work in
practice remains to be seen. Of course, at this stage, I'm willing to
stake my all on the results, but there is always a half-question until
the 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 been
said, on the very edge of Tinkle Creek. The banks were fairly solid
here, and descended precipitously to the water ten feet below. The
shores were about twenty feet apart.

"Suppose the spanners break when you're halfway over, Tom?" asked his
chum.

"I don't like to suppose anything of the sort. But if they do, we're
going down!"

"Can you get up again?"

"That remains to be seen," was the non-committal reply. "Well, here
goes, anyhow!"

Going up into the observation tower, which was only slightly raised
above the roof of the highest part of the tank, Tom gave the signal for
the motors to start. There was a trem