The dirigible from Fort Denton was not an unusual sight aloft, and consequently attracted but little attention from the people of the city; but out at the post Grail’s flight was watched with curious interest. Officers and men alike, although pretending indifference, laid aside their duties to follow, with eager gaze, the evolutions of the airship. They gained but little for their pains, however. Out over the line of smoky chimneys marking the water front they saw him go; then sail in a straight line across the river, where he turned to the south, and, having executed a couple of wide circles over the wildernesslike bottoms below the town, headed back for home. But as to his purpose they gathered not the slightest intimation. At that distance they could not discern that as he swept above the weed-grown, bush-covered lowlands so frequently subject to overflow, he leaned over in the car, and studied with the eye of the skilled topographer every feature of the country beneath him. Upon a tumble-down shack in a clump of stunted willows his gaze lingered longest, and as he estimated its distance from the river, as well as from the few other habitations which dotted the waste acres, his eye showed a glint of satisfaction. Unwilling, however, to reveal by his movements the nature of the survey he was making to any possible watcher, he did not hang long over the spot, or descend for a closer view, but contented himself with two rounds, at high altitude, as already described, and beat back westward toward the fort. With the wind against him, his return trip consumed more time than the outgoing one, and it was well after noon when he finally effected a skillful descent to the parade ground. He had been absent from the post altogether a little over two hours. “Has Sergeant Cato returned yet?” was the first question he asked as he sprang from the car; but, receiving a sullen negative for answer, bent his steps, as soon as he had seen the dirigible safely put away, toward the guardhouse. There he found himself confronted by Lieutenant Hemingway, who happened to be acting as officer of the day. The younger man’s eyes fell, and he showed his embarrassment by blushing painfully; but Grail was cool and steady as a statue. “I wish to speak to Private Simmons, placed under arrest by my orders,” he said brusquely. “Simmons?” Hemingway spoke rather superciliously. “Oh, yes--the man brought in from the balloon squad. Why, he isn’t here. I heard that there was only a slight disorderly charge against him, and I let him go to his quarters.” “You _heard!_” repeated Grail icily. “Didn’t you know the nature of the accusation against him?” The other manifested a shade of anxiety. “Why--er--no,” he stammered. “I was not here, you see, when the fellow was brought in, and just as I returned both the corporal and sergeant were called out by a fight over at barracks.” “And you did not consult the book before taking this step?”