side the latter was looking through a
pair of marine glasses they had fetched along, thinking they would prove
especially valuable in scrutinizing the country over which they might be
passing in the aeroplane.

"They're our friends, the revolutionists, I reckon," he announced. "I
can see several who carry big swords that dangle around their heels. And
the common soldiers, while they have little if any uniforms, and some of
them no shoes, seem to all have guns in their hands. Here, look and
tell me what that is on the little rise. I'm afraid our worst fears are
going to come true."

"Well, you're right, Andy," replied the other, after he had clapped the
binoculars to his eyes. "That's a cannon, all the same, and they're
getting ready to shoot!"

"Oh! my! It makes a fellow's flesh just creep, to think of being banged
away at with a great big cannon!" declared Andy.

"This one isn't so very big, I think. And now we're nearly opposite
where the fire burns. They're going to make a move to show their
hand. Drop down flat on the deck, Andy--quick with you!" and Frank, as
he spoke, set the example himself.

Hardly had the two boys thus thrown themselves down than there was a
heavy boom, accompanied by a brilliant flash of fire from the shore.

The revolutionists had fired upon the little steam yacht!

CHAPTER XII.

A GREAT SURPRISE.

"Wow! now, what do you think of that?" exclaimed Andy, raising his
head, just as one of the big turtles native to these warm waters might
thrust his out of his shell.

"Why, that was only a warning to bring us up short, and pay attention!"
declared Frank. "Because, as you saw, the ball splashed the water ahead
of our bow."

"But Frank, we don't mean to head across?" cried Andy, getting up on his
knees, the better to see.

"To be sure we don't. That was all settled long ago; and you notice that
our good Felipe is still keeping her nose headed straight upstream. Now
out goes the searchlight, just as we arranged. Wonder what they'll think
that means!"

"Perhaps they'll believe they knocked it overboard with that shot!"
suggested Andy, who could joke, even when facing troubles as thick as a
sea fog.

"Listen!" Frank exclaimed, "there's a chap with a pair of leather lungs,
shouting a lot of gibberish. I suppose he's demanding our surrender, and
threatening to blow us to smithereens if we decline to believe him."

"One good thing is that each minute takes us further up the riv