oked.

"What on _earth_ are those fellows doing?" he continued.

"Re-laying the road, perhaps."

"One doesn't re-lay a road by making a deep hole in it."

"Well--gas!"

"Gas and electric light mains in this street are all led along a special
conduit reached by manholes every eighty yards," said Champion. "There's
no need to dig."

"Well--drains!" said I vaguely. But I was a mere child in the hands of
this expert.

"The drains, as you call them," he said testily, "consist of a great
sewer away in the depths, accessible from various appointed places.
Besides, nobody in his senses tries to lift earth out of a hole with a
pick-axe."

"Perhaps the solution of the mystery lies inside the wigwam," I said.

"No. That is just what complicates matters. When a shaft leading down to
the electric light mains is opened, one of those canvas shelters is put
over the top. Now there is nothing under that shelter--nothing but the
bit of road it covers. The thing seems to be simply a stage accessory,
planted there to give the encampment an aspect of reality. Ah, look at
that!"

"That" was a small piece of paving-wood, dexterously hurled by the
dirty-faced boy, who seemed to be finding time hang rather heavily on
his hands. It took a passing citizen in the small of the back, but when
he swung round to detect the source of the missile the boy was on his
knees again industriously blowing up the brazier.

With an indignant snort the citizen passed on his way, doubtless adding
the outrage, in his mind, to the long list of unsolved London crimes.
But retribution awaited the youthful miscreant. The phlegmatic policeman
who was regulating the traffic on the single-line system happened to
notice the deed. He walked majestically across from the far side of the
street towards our excavating friends.

"Come on!" said Champion to me. "There's going to be some fun."

We stepped out through one of the windows, which possessed a broad
balcony, and took our stand behind some laurels in tubs which lined the
balustrade. The street was comparatively quiet at the time, and we were
able to hear most of the dialogue that ensued.

"'Ere, mate," began the traffic-expert to the smaller of the two
navvies, "just ketch that boy of yours a clip on the side of the 'ead,
will you?"

The smaller man desisted from his labours in the hole.

"Wotsye, ole sport?" he inquired cheerily.

The policeman was a little ruffled by this familiarity.

"I'll tro