“O-o-o-oh!” he murmured.

“What is it?” inquired the inventor, curiously.

“The very, wonder of the thing,” replied Benson, frankly, looking over the whole length of the “Pollard” as she lay propped up on the sturdy ways.

Nor did that simple speech make the inventor think any less of the boy.  Though Hal Hastings remained silent for some time, his fascinated gaze rested steadily on the strange-looking outlines of the cigar-shaped bull of the boat.

The outer hull was of steel plates, carefully riveted into place.  The entire length of the boat was about one hundred and ten feet, which in point of size placed her just about in the class of boats of this type which are being constructed to-day.

Near the center of the boat, on the upper side, was the conning tower, about nine feet in outside diameter, and extending some four feet above the sloping deck of the craft.  Around the conning tower extended a flat, circular “platform” deck.

At the bow of the boat the torpedo tube projected a short distance.  At the stern the rudder was in place, and all was in readiness for placing the propeller shaft and the propeller itself.  On the floor of the shed, near the middle of this strange, dangerous boat, lay miscellaneous small pieces of machinery and fittings.

At the starboard side of the boat stood a ladder that ascended to the platform deck.  In the top of the conning tower a man-hole cover stood propped up.  It was through this opening that the workmen entered or left the boat.

From outside the shed several wires ran in.  In dark weather these wires carried the current for electric lights in shed and boat.

“I won’t ask you aboard until the foreman and other workmen arrive,” explained Mr. Pollard.  “It’ll be only a few minutes to wait.”

While they were still examining the outer hull, and discussing the submarine, Dan Jaggers, in his workman’s clothes, reached the open doorway of the shed.  One look inside, and he halted short.  He gathered from the talk he heard that Jack Benson and Hal Hastings were to be added to the “Pollard’s” working gang.

“Not if I know myself—­and the foreman—­and I think I do!” growled the Jaggers youth, backing away unseen.

The next of the workmen to arrive was Michael O’brien, red-haired and about twenty-eight years of age.  He was good-humored and talkative, and the two boys took an immediate liking to him.

Through the gate of the yard came Joshua Owen, a man of forty-five, of medium height, broad-shouldered, black-haired and with a frame that spoke of great physical power and endurance.  Yet he had restless, rather evil-looking eyes.  He did not look like the sort of man whom a timid fellow would want for an enemy.

“Hold on there, Unc,” greeted Dan Jaggers, motioning his foreman-uncle aside.  “Say, you know that cheeky young fellow I told ye about—­the tricky one that played the sneak on me, and gave me this black eye?”