Thus matters went along most smoothly.  Jack Benson and Hal Hastings, with a good general knowledge of mechanics, and willing to work hard and tackle new problems, were learning much.  Even before the “Pollard” was launched and sent on her trial trip these two boys showed remarkable proficiency in equipping and handling this wonderful class of craft.

In the meantime the boys had left the hotel, taking up their quarters at a comfortable boarding-house where Foreman Andrews lived.  Though Farnum was paying them fair wages, they were thrifty enough to be on the lookout for any outside work with their camera outfit.  So it happened that, one evening after supper, Jack and Hal, carrying their outfit, set out on a walk of more than two miles.  They had secured an order to go to a wealthy man’s summer “cottage,” as the great, handsome pile was called, there to make some flashlight photographs of some of the large, expensively furnished rooms.

Time flew, and the owner of the cottage caused many delays by wishing furniture shifted about before the photographs were made.  It was after eleven o’clock at night when the two submarine boys left the cottage to tramp back to Dunhaven.  As they neared the village they heard the town clock striking midnight.  That was the only sound they could hear besides the movement of their own feet.  Dunhaven was wrapped in sound slumber.

Their way led the boys close to Farnum’s boatyard.  As they came around a corner of the fence, Hal, who was slightly in the lead, stepped back quickly, treading on his friend’s toes.

“Sh!” whispered Hastings.  “Keep quiet and take a sly peep around the corner.  Look up along the fence and see what you make out.”

Slipping off his hat, Jack took a hasty look, exposing very little of his head, while Hal now crowded close to him from behind.

“Someone trying to scale the fence,” whispered Jack.  “By Jove, there he goes.  He has a good hold, and is going—­now he’s over in the yard.”

Such stealthy prowling could mean little else than mischief brewing.  To both the boys came instantly the same thought: 

“The submarine boat!”

“Did you recognize him?” whispered Hal, quivering.

“No; too dark for that, and, besides, he was too quick.  But we must hustle to alarm someone.”

“There’s a watchman in the yard,” Hal replied.  “He ought to be getting busy.”

“I don’t hear any hail, or any shot,” Jack replied.  “Hal, old fellow, we’ve got to do something ourselves.”

“Well, we can climb the fence as well as that stranger did.”

“We’d better.  Here, take the flashlight gun.  Pass that and the camera up as soon as I get to the top of the fence.  We can’t leave our outfit outside—­it’s worth too much money.”

With that Jack Benson swiftly found a knothole in which he could get a slight foot-hold.  With that start he was quickly up on top of the ten-foot fence.  Bending down he took camera and flashlight “gun.”  Hal hurriedly followed.  Down in the yard, they started speedily though softly forward, going by impulse straight toward the submarine’s shed, though keeping in the shadow of other buildings.