“I suppose they’re hoping they will to-day, whatever the test is to be,” muttered Hal Hastings.

Fifteen minutes more passed.  Then a little flock of six-oared cutters left the side of the gunboat “Oakland.”  In the stern-sheets of each cutter sat a naval officer in uniform.

“There’s Lieutenant Danvers,” cried Jack, eagerly.  “He brings us our instructions, whatever they are.”

In a few moments more Danvers was along side, making his way up to the platform deck.  In his right hand Danvers carried an official looking sealed envelope.

In his eager curiosity Jacob Farnum extended a hand to take the envelope, but Danvers drew it back.

“Pardon me,” murmured the shipbuilder, confusedly.  “I should have known better.  The communication is, of course, for the captain.”

Danvers turned the envelope over to Captain Jack Benson, who broke the seal, drawing out the paper enclosed.  This is a part of what the submarine boy read aloud: 

"’The Navy Department has just reported, by wireless, that a semi-submerged derelict, evidently that of a three-master schooner, is drifting in the paths of navigation at a point 385 miles southwest by south of this present station.  The Department suggests that it would afford an example of practical use for submarines, if those now on this station would accompany a gunboat, at full speed for cruising, and attempt to discover and blow up this derelict.’"

“Great!” glowed Eph.  “I vote for it.”

“So do those on the other boats, if the observable excitement is to be taken as an indication,” laughed Mr. Farnum.

“This letter goes on to request,” announced Benson, “that the commander of each submarine willing to enter this affair signal to the ‘Oakland’ by hoisting the signal ‘Ready.’  Do you hear that, Eph?”

Somers made a dash for the signal chest.  In another moment the appropriate bit of bunting was fluttering on the halliard at the top of the signal mast.

“We are directed,” Jack read on, “to be ready within thirty minutes.  We must follow the ‘Oakland’ down the bay at a cruising speed of sixteen miles an hour.  Once out of the bay, the ‘Oakland’ will signal our formation to us.”

“Do you see the boat the Rhinds signal is going up on?” laughed Hal Hastings.  “It is going up on the submarine ‘Thor.’  According to the old Norsemen tales Thor was The Thunderer—­also the fellow who struck with the big hammer.  It looks like a Rhinds boast that they are to do big things on this lightning cruise.”

“Yes; Thor was an old Norse god,” muttered Captain Jack.  “And the early Norsemen were very largely pirates.  Perhaps we are to take the signal on the ‘Thor’ as an intimation that Rhinds is out to play pirate in earnest on this cruise.”

As Benson uttered these words he felt an odd little shiver run over him.  Yet he gave it no more thought.  Little idea had he, at that moment, how prophetic his words were likely to be!