“Since you know so much about the 1804 dollar,” went on Milo, catechizingly, “perhaps you know why it is so rare?  Or perhaps you didn’t add a study of American history to your numismatics?”

“The commonly accepted story goes,” said Brice, taking no heed of the sneer, “that practically the whole issue of 1804 dollars went toward the payment of the Louisiana Purchase money, when Uncle Sam paid Napoleon Bonaparte’s government a trifle less than $15,000,000 (or under four cents an acre) for the richest part of the whole United States.  Payment was made in half a dozen different forms,—­in settlement of anti-French claims and in installment notes, and so forth.  But something between a million and two million dollars of it is said to have been paid in silver.”

“Are you a schoolmaster, Mr. Brice?” queried Milo, who seemed unable to avoid sneering in futile fashion at the man who was dominating his wavering willpower.

“No, Mr. Standish,” coolly replied the other.  “I am Gavin Brice, of the United States Secret Service.”

Standish’s bearded jaw dropped.  He glanced furtively about him, like a trapped rat.  Gavin continued, authoritatively: 

“You’ve nothing to fear from me, as long as you play straight.  And I’m here to see that you shall.  Two hours ago, I was for renouncing my life-work and throwing over my job.  Never mind why.  I’ve changed my mind, now.  I’m in this thing to the finish.  With Hade out of the game, I can see my way through.”

“But—­”

“Now I’ll finish the yarn you were so gradually leading up to with those schoolboy questions of yours.  French statesmen claimed, last year, that something over a million dollars of the Louisiana purchase money was never paid to France.  That was money, in the form of silver dollars, which went by sea.  In skirting the Florida coast—­probably on the way from some mint or treasury in the South—­one or more of the treasure ships parted from their man-o’-war escorts in a hurricane, and went aground on the southeastern Florida reefs.  The black pirate, Caesar, and his cutthroats did the rest.

“This was no petty haul, such as Caesar was accustomed to, and it seems to have taken his breath away.  He and his crew carried it into Caesar’s Estuary—­not Caesar’s Creek—­an inlet, among the mangrove swamps.  They took it there by night, and sank it in shallow water, under the bank.  There they planned to have it until it might be safe to divide it and to scatter to Europe or to some place where they could live in safety and in splendor.  Only a small picked crew of Caesar’s knew the hiding place.  And, by some odd coincidence, every man of them died of prussic acid poisoning, at a booze-feast that Caesar invited them to, at his shack down on Caesar’s creek, a month later.  Then, almost at once afterward, as you’ve probably heard, Caesar himself had the bad luck to die with extreme suddenness.

“The secret was lost.  Dozens of pirates and of wreckers —­ancestors of the conchs—­knew about the treasure.  But none of them could find it.