the hidden life that
filled the great jungles. There came a high shrill yell from one bank,
to which Mbopo replied, and the boys knew that once more they were among
the black dwarfs. This was repeated in the afternoon, but even by the
aid of their glasses they could not make out who had hailed them.

Only once did they meet with trouble. This occurred when Critch ran
aground on a hidden shoal. The solid raft ran deeply into the mud of the
river bottom and it took the efforts of both crews to get her off.

For three days more they floated down the river, but on the third
evening both boys noticed signs of uneasiness among the pigmies. In the
morning, before the start, Mbopo approached Critch.

"Where Buburika Mac?" he inquired, glancing around as if he expected to
find Captain Montenay in their vicinity. Critch glanced at Burt.

"Him down there," and he waved his hand downstream. Mbopo looked
doubtfully around.

"Mbopo no like vera good," was his reply. "Him Zwengi pretty quick."

"Zwengi?" repeated Critch, puzzled.

"Him vera bad," declared Mbopo. "Him big, much fight. Mbopo no like."

"Must be a tribe they're at war with," said Burt. He took up the rifle
and turned to the chief. "Him kill Zwengi."

"Mwanzi kill Zwengi?" asked Mbopo of Critch, plainly putting all his
faith in the latter's prowess. Critch laughed and nodded. Mbopo turned
and spoke joyfully to his men, who instantly lost their uneasy
appearance and sprang aboard with a shout of delight.

"It's up to you," grinned Burt, and Critch nodded soberly.

"Plain bluff again," he said. "If we are held up, those bows o' the
dwarfs ought to get in good work, an' your three cartridges'll help a
whole lot unless the Zwengi have guns. If they have, it's all up, I
guess."

"The Makua can't be so very far off now," replied Burt. "The river's
getting bigger and bigger, and the current's swifter. S'pose we could
rig up any kind of breastwork on the rafts?"

"Better not waste time trying," dissented Critch. "I'm afraid of making
them top-heavy. Well, let's be off. We ought to hit the Makua pretty
quick now. If we don't meet Cap'n Mac I expect Mbopo'll be sore. That's
what's worrying me right now."

It was worrying Burt too, but he jumped aboard his raft and cast loose
without giving vent to his fears. He realized only too well that the
Zwengi might have canoes, and if they were discovered and pursued their
only hope was to beat off the enemy.

For several