"Thank you, sir," was Henri's modest acknowledgment.
"It is with the Zeppelin I navigate," advised the captain. "You know it not?"
"Not much," put in Billy, "though we once dangled on the anchor of one, and another time I fell with a monoplane right across the back of one of your dirigibles."
"Yes," remarked Henri, "and if it hadn't been for that, there wouldn't have been any Billy alive to tell about it."
The captain showed a disposition to continue his talk during the afternoon with the boys, but a new arrival of evident importance interrupted. This addition to the party was a much older man than the rest, wore a military cloak, and his long, gray mustache curled at the ends in close touch with his ears. As he stood at the end of the big table, now cleared of its cloth, and rested a hand, enveloped in a gauntlet, upon the shining surface, everybody in the room saluted. Over the shoulder of this distinguished guest the boys saw the face of Roque.
As if by signal, further increased by the hasty entrance of three additional numbers, the attending company ranged by equal division on each side of the table, and all followed the directing movement of the man at the head of the board in seating themselves.
Billy and Henri were the only bystanders, for though Spitznagle had not ventured to flop down upon a bench at the table, he perched himself on a high stool, completely blocking the door leading into the pantry.
One of the short men who had first appeared with Capt. Groat produced a capacious wallet, and laid out in orderly array a number of neatly folded papers which had been contained in the leather.
"This is the navigator detailed to determine air currents, sir," explained Roque to the chief figure, at whose right elbow the secret agent was stationed.
The man in the cloak fixed his gaze on the expert with the notes. The latter accepted this as permission to speak, and read in precise manner the results of close observation during a recent aërial expedition of Zeppelins, escorted by armed German biplanes, in the vicinity of Dover straits.