"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.