ve they are going to damage the weapons in some way or other,"
Jack answered, "and in that case they will certainly use explosives. I
came over to ask you to join us at a spot where we can see everything.
The sentries on the guns show well up against the sky-line, so that when
these fellows get on their feet we can see at once when they move. By
the way, it would be wise to warn the gunners to be careful when the
time comes for using their weapons."

"Yes, I'll do that," exclaimed the officer. "Who knows! these spies may
fix a charge of dynamite. Wait here a moment while I give the order."

A few minutes later he joined Jack once more, and both crept to Guy's
side and then moved forward, for Piet Maartens and his companions had
crawled closer to the guns. Raising their heads cautiously, they peeped
over a bank and saw the guns, only a few yards in front of them,
standing dimly defined against the star-lit sky, while close beside them
crouched the Boer spies.

Piet Maartens lay a few yards in front upon the edge of the hill, and as
Jack and his friends watched him they saw him lift his head and look
steadily in either direction, and then turn round as if to make sure
that he was unobserved.

Instantly all three sank flat on the ground, but a minute later, when
they peered over the bank again, he was facing down the hill, and as
they looked, he stood up and produced what was evidently a pair of
field-glasses and applied them to his eyes.

"He's trying to make out where the pickets are," whispered Jack. "Keep
down, you fellows, he's turning this way now."

"He can look as long as he likes," chuckled the young officer, "but he
won't see a single man beyond the regular outposts. I ordered all my
fellows to lie flat and remain without a move till they hear me shout."

"That's good," muttered Jack. "Halloa! what's that?"

As Jack spoke, one of the Boer spies gave a low warning hiss between his
teeth, and a second later a corporal and two men swung by in the
darkness on their way to relieve an outlying picket. They had
approached so silently that Piet Maartens was taken by surprise, and was
instantly perceived. But his coolness did not desert him. He instantly
replaced his glasses and challenged.

"Relieving picket," shouted the corporal, and passed on without a halt.

"Pass, relieving picket. All's well," Piet Maartens answered, and,
having waited a minute, again produced his glasses.

Five minutes late