Obenreizer listened for a moment, and started back from the door.

“I know!” he exclaimed.  “I heard of this when I was apprenticed here at the watchmaker’s.  Perrin Brothers have finished their famous clock-lock at last—­and you have got it?”

“Bravo!” said Maitre Voigt.  “The clock-lock it is!  There, my son!  There you have one more of what the good people of this town call, ’Daddy Voigt’s follies.’  With all my heart!  Let those laugh who win.  No thief can steal my keys.  No burglar can pick my lock.  No power on earth, short of a battering-ram or a barrel of gunpowder, can move that door, till my little sentinel inside—­my worthy friend who goes ‘Tick, Tick,’ as I tell him—­says, ‘Open!’ The big door obeys the little Tick, Tick, and the little Tick, Tick, obeys me.  That!” cried Daddy Voigt, snapping his fingers, “for all the thieves in Christendom!”

“May I see it in action?” asked Obenreizer.  “Pardon my curiosity, dear sir!  You know that I was once a tolerable worker in the clock trade.”

“Certainly you shall see it in action,” said Maitre Voigt.  “What is the time now?  One minute to eight.  Watch, and in one minute you will see the door open of itself.”

In one minute, smoothly and slowly and silently, as if invisible hands had set it free, the heavy door opened inward, and disclosed a dark chamber beyond.  On three sides, shelves filled the walls, from floor to ceiling.  Arranged on the shelves, were rows upon rows of boxes made in the pretty inlaid woodwork of Switzerland, and bearing inscribed on their fronts (for the most part in fanciful coloured letters) the names of the notary’s clients.

Maitre Voigt lighted a taper, and led the way into the room.

“You shall see the clock,” he said proudly.  “I possess the greatest curiosity in Europe.  It is only a privileged few whose eyes can look at it.  I give the privilege to your good father’s son—­you shall be one of the favoured few who enter the room with me.  See! here it is, on the right-hand wall at the side of the door.”

“An ordinary clock,” exclaimed Obenreizer.  “No!  Not an ordinary clock.  It has only one hand.”

“Aha!” said Maitre Voigt.  “Not an ordinary clock, my friend.  No, no.  That one hand goes round the dial.  As I put it, so it regulates the hour at which the door shall open.  See!  The hand points to eight.  At eight the door opened, as you saw for yourself.”

“Does it open more than once in the four-and-twenty hours?” asked Obenreizer.

“More than once?” repeated the notary, with great scorn.  “You don’t know my good friend, Tick-Tick!  He will open the door as often as I ask him.  All he wants is his directions, and he gets them here.  Look below the dial.  Here is a half-circle of steel let into the wall, and here is a hand (called the regulator) that travels round it, just as my hand chooses.  Notice,