e went on.

"He is believed to have two in the hands of the Mexican Federal
Army," Lieutenant Trent continued. "I have just heard that, if
we send a landing party ashore on a hostile errand, on each warship
an officer and a squad of men will be stationed by a searchlight
all through the dark hours. That searchlight will keep the skies
lighted in the effort to discover an airship."

"And we ought to be able to bring it down with a six-pounder shell,"
Danny Grin declared, promptly.

"There is a limit to the range of a six-pounder, or any other
gun, especially when firing at high elevation," Trent retorted.
"An airship can reach a height above the range of any gun that
can be trained on the sky. For instance, we can't fire a shell
that will go three miles up into the air, yet that is a very ordinary
height at which to run a biplane. Have you heard that, a year
or more ago, an English aviator flew over warships at a height
greater than the gunners below could possibly have reached? And
did you know that the aviator succeeded in dropping oranges down
the funnels of English warships? Suppose those oranges had been
bombs?"

"The warship would have been sunk," Darrin answered.

"Huerta's bird men might be able to give us a surprise like that,"
Trent suggested. "That may prove to be one of the new problems
that we shall have to work out."

"Oh, I've worked that out already," yawned Danny Grin. "All we
have to do is to equip our funnels with heavy iron caps that will
not interfere with the draft of the furnaces, but will keep any
oranges---bombs, I mean---from dropping down the funnels."

"All right then," added Lieutenant Trent. "We will consider Dalzell
has solved the problem of keeping bombs out of our funnels. What
is Dalzell going to do about contact bombs that might be dropped
on deck or superstructure of a battleship?"

"All I can see for that," grinned Dan, "is to call loudly for
the police."

"One biplane might succeed in sinking all the warships gathered
at Vera Cruz," Trent continued.

"Was that the thought that made you look so happy when you came
in here?" Dan asked, reproachfully. "The thought that you could
scare two poor little ensigns so badly that they wouldn't be able
to sleep to-night?"

"That was far from my plan," laughed Trent. "What I am really
happy about is that, the way affairs are shaping, we shall soon
be studying real war problems instead of theoretical ones."

"The ques