Among the villagers it was said that the physician and his disciple were guarded closely night and day, and that the Paduan certainly would be burned at the stake if he did not succeed in making gold.  Country folk had seen the stake set up and the faggots piled.  In case the wizard proved a false prophet Gregory meant to make the execution as public as possible.

Padraig explained that the final trial must take place inter canis et lupus—­between dog and wolf—­in that hour which is neither daylight nor dark.  As dusk fell the knights and esquires of the Temple ranged themselves in orderly ranks along the walls, at some distance from the door of the underground chamber.  The low archway was now open; the glow of a brazier showed red against the rear wall.  Torches lighted the stone-paved yard, and beyond the open gate the white faces of peasants crowded, awe-stricken and expectant.  When the physician was brought out by the guards to a seat near the stake, the sobs of a woman were heard in the outer darkness.  Padraig, following, cast a swift glance through the gate and saw the dim shapes of horsemen outlined against the sky.

Last of all appeared the Preceptor and Prince John with their immediate followers, and took their seats midway in the ranks of onlookers, directly opposite the door, where they could see every stage of the proceedings.  Gregory, furtively scanning the face of the physician, saw therein not a sign of fear.  Padraig advanced into the open space before the cellar, and bowed to Prince John and the Preceptor.  Then from a niche within the door of the chamber he lifted a large crucible, and a siffle of indrawn breath was heard in the crowd as he carried it toward the fire.  Gathering pitchy twigs and chaff from a heap of fuel he packed them deftly into the open top, and set the jar on the brazier, returning then to the side of Tomaso.

The minutes passed but slowly.  The nerves of all the spectators were strung to the snapping-point.  Gregory finally began to explain to Prince John, who looked half curious and half skeptical,—­

“This crucible, your Grace, is now throwing off the vapors generated by fervent heat.  When these have been absorbed by the chaff above, the gold will be found beneath.  The possibilities of this priceless formula are not as yet altogether known.  We do not know what may come to light.  You may be astounded—­”

The chaff in the crucible caught fire from a wisp that thrust up into it from the brazier, flared up of a sudden and lighted every corner of the old cellar.  It revealed the craning neck and slack jaw of Gregory, the covetous glittering eyes and incredulous smile of Prince John, the scared faces of the huddling peasants.  Then there was a crash that shook the earth.  Battlements rocked, pavements cracked, blocks of stone leaped into the air like a fountain of masonry.  When fire encounters high explosives in a tunnel the results are remarkable.  Torches dropped or were blown out, and stumbling, cursing men ran right and left—­anywhere to escape the pelting stones.  Padraig, holding to his master’s arm, guided him out of the gate and toward the sound of trampling hoofs upon a little hillock.  There they found Edrupt, Guy and Alan struggling with their frantic horses.  Swart came up with two more horses, and soon the party was beyond all danger of pursuit.