Behind them and to one side, centurions shouted hoarsely as their squads began to raise and swing the hollowed timber on which rested all hopes of success. The trunk that had given Vibulenus the idea, a hundred and twenty feet long and straight as a die, had been chosen to execute the plan as well. Legionaries had sawed the trunk in half lengthwise and hollowed it with adzes so quickly that the tribune himself marveled.

On the estate of the Vibuleni, such labor would have been performed by slaves-less well, and taking three or four times as long to accomplish. They were slaves, every man in the legion, and at some level they all knew it; but they didn't think like slaves. There were citizens of Rome and the best soldiers in the world, despite the vagaries of a consul who should have stuck to politics and similar forms of extortion.

"Pace, boys, don't let the bitch slide," Clodius ordered, his voice showing the strain of physical effort if not of fear. The gangway was narrow. If they let gravity carry a corner of the gallery over the side, they were well and truly fucked. The crossbows that sank bolts vainly in the mud roof would turn the force into a score of shrieking pincushions before any of them could be untangled from the overturned gallery.

Behind them, present only in their prayers, the log weapon was being swung into position. Like the gangway, it pivoted in a socket dug into the ramp, but the teams which lifted it did so through hawsers attached to a pair of shear legs. The hundreds of men hauling back on each hawser were covered by equal numbers of legionaries with raised shields, adequate protection for targets near the extreme range of the defenders' bows.

Nobody knew it all, thought Vibulenus as the archers in the tower shifted their aim from the gallery to the teams of men swinging the hollow log. The army Crassus marched into Parthia thought it had all the answers to war, but the squadrons of horse archers supplied with camel-loads of arrows had battered the legions the way the waves defeated a cliff.

But the furred, quick-handed autochthones of this place did not have all the answers either, despite their ability to spew flame as a fountain spurts water. Their missile weapons depended on the tension of bent wood. Real artillery powered by torqued skeins of ox sinew would have slaughtered the lightly-protected lifting teams faster than they could be replaced.

As the shear legs straightened toward vertical, the forward end of the log angled upward to the height of the tower's battlements. A third crew, protected by the rampart, marched along the guardwalk hauling a chain that drew the end of the device sideways. The log now formed the hypoteneuse of a right triangle whose straight sides were the platform of the siege works and the face of the tower.

The defenders must have expected the log to be used as a ram. Even now, as it lifted to an unexpected angle which displayed the hollow interior lined with bronze sheet, it looked more like a ram than it did anything else in their experience-or in the experience of the Romans who had built and were about to use the device.

At the base of the pivoting log was a high screen of wicker and leather. It covered a final crew of legionaries, leavened this time with a few local auxiliaries, and the great bellows made from whole oxhides. One of the auxiliaries gave a high-pitched order as the log steadied into position. The men on the arms of the bellows poised, but only when the centurion relayed the command in a parade-ground bark did a pair of legionaries grip the handles of a pottery jar and lift it toward the broad funnel mounted on the base of the log.

Liquid spouted from the top of the tower. It had began to burn halfway along its course toward the mobile gallery.

Vibulenus and his fellows had staggered off the lower end of the gangway, to the glassy remnants of the original siege ramp. At the tribune's first step, his leg crunched through what had seemed to be firm ground. It was like walking through a crusted snowdrift, except that the edges drew blood as they scraped Vibulenus' calf.

The gallery dipped forward as other Romans broke through as well. The fire had consumed everything flammable in the siegeworks; but wherever there was enough silica in the earth to vitrify, glass had kept the fill from setting under its own weight and the heavy rains. The sprawled remnants were not impassible, but they provided a barrier of hidden pits covering half of the last twenty feet between the new ramp and the base of the tower.

And that saved the lives of the men in the gallery.

The defenders were expert in their use of flame, so expert that the first gout of blazing fluid travelled from the spout with the conflicting pulls of gravity and outward inertia in an arc calculated to splash it under the roof of the gallery. The autochthones knew that by flooding the area when the assault force was directly beneath, they could destroy the legionaries as completely as they had the first siege ramp-but there was no need to runnel flame over the refractory roof of the gallery if the clinging, erosive liquid could be splashed onto the legs of the men inside.

The gallery wobbled to a halt three feet short of where the defenders expected it when they started their flame on its long fall.

Vibulenus' calves itched in a way that was more intrusive than any pain could be. Sweat that raced down his thighs paused and burned when it reached the grit and abrasions on his lower legs. He could not take a hand from the bar he carried to scratch the affected area. His palms were hot and the skin of them, though calloused by swordhilt and shield strap, slipped over the muscle and bone beneath. The unusual stress of carrying the gallery was reducing his hands to puffy, bleeding blisters.

The tribune could see only dimly. The assault force was in an artificial valley between the siege ramp and the sheer wall of the tower. Most of what sunlight did scatter through was blocked by the sheltering roof, and even the remainder was blurred by the sweat and tears which Vibulenus could not wipe away. The tumbling flame, striking and splashing before the gallery, instantly returned light and color to a microcosm of gray pain.

"Mother!" screamed Clodius, loud enough for the tribune to hear him and be surprised. Everybody was shouting, though, and the flames roared as they splattered and eroded the earth. The fire was deep red, with flecks of quicklime as white as rage and a shroud of ragged smoke that was visible only at a distance from the bubbling flame.

The gallery grounded before anyone had the presence of mind to order it down. Hands dropped the bars in panic as the men of the assault force tried to jump back. They tangled themselves with the structure and the men behind them.

A legionary in the fifth row did manage to leap out the rear of the shelter. Sunlight and the imprisoning hugeness of the structures before and behind drove the man back under the roof of a moment later. He brushed off his helmet on the eaves. As it rolled on the blackened rubble, a dozen quarrels snapped toward and clangingly against it.

"All right," ordered Gaius Vibulenus. His voice was as cool as the core of him which shock had disconnected from the sweating, punished body he wore. Clodius Afer and the other men in the front rank were being burned by the pool of fire which closed their end of the gallery, and the tribune's own shins were scorching. "We're going to side-step left, now. Take your bars and lift!"

He should have worn his greaves… and he was so disoriented that he almost failed to obey the orders he had given the men who were suddenly under his actual control.

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.