engines,” pursued the officer in charge.

Jack and Hal were both worried. The sudden break had a bad look for the
Pollard boats, in the success of which these submarine boys were most
vitally interested.

At last, from below, the suspected parts of the engine were reported to be
cool enough for examination. The naval officer in charge followed Jack and
Hal below.

Taking off his uniform blouse and rolling up his sleeves, Hal sailed in
vigorously to locate the fault. Machinists and cadets stood about, passing
him the tools he needed, and helping him when required.

At last, after disconnecting some parts, Hal drew out a long, slender
brass piston.

As he held it up young Hastings’s face went as white as chalk.

“Do you see this?” he demanded, hoarsely.

“Filed, crazily, and it also looks as though the inner end had been heated
and tampered with,” gasped Jack Benson.

“This, sir,” complained Hal, turning around to face the naval officer in
charge, “looks like a direct attempt to tamper with and damage the engine.
Someone has done this deliberately, sir. It only remains to find the
culprit.”

“Then we’ll find out,” retorted the naval officer, “if it takes a court of