The gallery bucked convulsively and grounded again as the sideways shift tripped several legionaries over the outstretched legs of their fellows. All the horns and trumpets in the legion brayed simultaneously while the shelter lurched another step away from the flames.
The ground shook as a huge fireball ignited on the roof of the tower. It was so bright that it shadowed the receding pool of flame near the assault force.
Ever since the gallery began its tortoiselike advance, the tribune had been too caught up in his immediate surroundings to think about the larger aspects of his plan. The professionals of the legion, rank and file as well as the centurions, had done their job with the stolid excellence of a grist mill grinding away its allotted task.
When Rusticanus gave the signal, two soldiers poured their jug of enhanced naphtha into the breech of the log. The local officer who advised on the process had suggested igniting it with water to spark on the quicklime. The legionaries had chosen to risk an open flame instead, something they understood as they did not understand starting fires with water.
The centurion in charge stepped to the log when the legionaries jumped back. He thrust a torch into the funnel glistening with the residue of thickened fluid. Fire bloomed from the touchhole.
“Bellows!” ordered Rusticanus.
Horns and trumpets cried out in a cacaphony intended to terrify the enemy rather than communicate orders. As the sky echoed, the twenty strong men on each lever of the bellows began to stride forward, ramming the air in the oxhide chamber into the base of the hollow log and the fire already blazing there.
Flame spurted twenty feet in the air from the touch-hole before a pair of soldiers clamped a bronze plug down on it. The air surging from the bellows mixed with the fluid and rammed it toward the open end of the tube over a hundred feet in the air. When oxygen bubbled into and through the burning liquid, the combination puffed explosively up the hollow trunk — and out, in an orange-red flash, across the defenders on the top of the tower.
The spurt was of superheated gas, not fluid that clung with the tackiness of pitch and molten sulphur, but it crinkled the bowstaves, armor, and faces of those archers it enfolded as they crouched at embrasures. The two defenders pouring liquid through a spout wailed and dropped their open vat as flame burst from it to meet the puff expanding from the hollow log.
There were several hundred additional gallons of fluid on the tower in closed containers which shattered when spreading fire wrapped them. When half the jars had ignited in a matter of seconds, the remainder exploded simultaneously. Part of the crenellations, fragments of equipment, and the bodies of defenders too fiercely ablaze to be recognized as living things rained in all directions from the top of the tower.
The flare mounted in a hemisphere, like the cap of a mushroom thrusting itself through the loam, until it broke free of the stone and wrapped in upon itself to climb still higher on the reflected heat of its own combustion. The platform from which it had lifted was bare of any form of life save the few defenders who still thrashed in the blazing sheet which had devoured their eyes and lungs already.
Vibulenus knew his weapon had been successful when an object slammed the sloping roof of the gallery and bounced, then fell again to the ground before the assault force. It could have been a burning missile, heavy enough that its shock grounded the shelter again. What sprawled in a smokey wrapper of flames was not a timber, however, but a corpse that had been a crossbowman before his flesh melted and heat cracked the phial in which he dipped his quarrels. The resinous poison burned blue.
“All right!” ordered Clodius Afer in a voice burned skeletal by emotion and flame-dried air. “Left on the count, boys, and put your backs —”
“Out the front with your tools, men,” said Vibulenus, speaking from a mind where everything had a place, like the markers of a board game awaiting the next shake of the dice cup.