“And if he fights most of the Mexicans will probably stand by him,” Dalzell contended.  His only hope of saving his own skin lies in provoking Uncle Sam into sending a spanking expedition.  At the worst, Huerta, if badly beaten by our troops, can surrender to our commander, and then he’ll have a chance to get out of Mexico alive.  If Huerta gave in to us, he would have all the Mexican people against him, and he’d only fall into the hands of the rebels, who would take huge delight in killing him offhand.  It’s a queer condition, isn’t it, when Huerta’s only hope of coming out alive hangs on his making war against a power like the United States.”

“Open for callers?” inquired Lieutenant Trent’s voice, outside Dan’s door.

“Come in, by all means,” called Ensign Dalzell.

Lieutenant Trent entered, looking as though he were well satisfied with himself on this warm April day in the tropics.

“You look unusually jovial,” Dan remarked.

“And why shouldn’t I?” Trent asked.  “For years the Navy has been working out every imaginable problem of attack and defense.  Now, we shall have a chance to apply some of our knowledge.”

“In fighting the Mexican Navy?” laughed Dave.

“Hardly that,” grinned the older officer.  “But at least we shall have landing-party practice, and in the face of real bullets.”

“If Huerta doesn’t back down,” Dave suggested.

“He won’t,” Danny Grin insisted.  “He can’t—–­doesn’t dare.”

“Do you realize what two of our greatest problems are to-day?” asked Lieutenant Trent.

“Attack on battleships by submarines and airships?” Dave inquired, quietly.

“Yes,” Trent nodded.

“Huerta hasn’t any submarines,” Dan offered.

“We haven’t heard of any,” Trent replied, “Yet how can we be sure that he hasn’t any submarine craft?”

“He has an airship or two, though, I believe,” Dave 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?”