across an open space between files of men in black, and realised before Ostrog spoke that he was looking down on the upper surface of latter-day London.  The overnight snows had gone.  He judged that this mirror was some modern replacement of the camera obscura, but that matter was not explained to him.  He saw that though the file of red figures was trotting from left to right, yet they were passing out of the picture to the left.  He wondered momentarily, and then saw that the picture was passing slowly, panorama fashion, across the oval.

“In a moment you will see the fighting,” said Ostrog at his elbow.  “Those fellows in red you notice are prisoners.  This is the roof space of London—­all the houses are practically continuous now.  The streets and public squares are covered in.  The gaps and chasms of your time have disappeared.”

Something out of focus obliterated half the picture.  Its form suggested a man.  There was a gleam of metal, a flash, something that swept across the oval, as the eyelid of a bird sweeps across its eye, and the picture was clear again.  And now Graham beheld men running down among the wind-wheels, pointing weapons from which jetted out little smoky flashes.  They swarmed thicker and thicker to the right, gesticulating—­it might be they were shouting, but of that the picture told nothing.  They and the wind-wheels passed slowly and steadily across the field of the mirror.

“Now,” said Ostrog, “comes the Council House,” and slowly a black edge crept into view and gathered Graham’s attention.  Soon it was no longer an edge but a cavity, a huge blackened space amidst the clustering edifices, and from it thin spires of smoke rose into the pallid winter sky.  Gaunt ruinous masses of the building, mighty truncated piers and girders, rose dismally out of this cavernous darkness.  And over these vestiges of some splendid place, countless minute men were clambering, leaping, swarming.

“This is the Council House,” said Ostrog.  “Their last stronghold.  And the fools wasted enough ammunition to hold out for a month in blowing up the buildings all about them—­to stop our attack.  You heard the smash?  It shattered half the brittle glass in the city.”

And while he spoke, Graham saw that beyond this area of ruins, overhanging it and rising to a great height, was a ragged mass of white building.  This mass had been isolated by the ruthless destruction of its surroundings.  Black gaps marked the passages the disaster had torn apart; big halls had been slashed open and the decoration of their interiors showed dismally in the wintry dawn, and down the jagged walls hung festoons of divided cables and twisted ends of lines and metallic rods.  And amidst all the vast details moved little red specks, the red-clothed defenders of the Council.  Every now and then faint flashes illuminated the bleak shadows.  At the first sight it seemed to Graham that an attack upon this isolated white building was in progress, but then he perceived that the party of the revolt was not advancing, but sheltered amidst the colossal wreckage that encircled this last ragged stronghold of the red-garbed men, was keeping up a fitful firing.