As Ballista watched, a six-pound stone moving almost too fast to see crashed into one of the screens shielding the bricklayers. Splinters flew, a cloud of dense dust erupted, the screen seemed to buckle, yet it remained in place. Another one or two of those and that will be another gone: more dead reptiles, and another delay.
Ballista ducked back behind the parapet. He sat down, resting his back against it, thinking. Every night the Sassanids withdrew to start again the next morning. Why? Why did they not work through the night? They had the manpower. If Ballista had been their commander they would have done. The northerner had read somewhere that under the previous eastern empire, that of the Parthians, there had been a reluctance to fight at night. Maybe it was the same with their Persian successors. Yet they had been digging the mine from the ravine at night. Possibly it took something special to drive them to it. It was a mystery – but war was one long series of inexplicable events.
'I have seen all I need for now. Let us go down.' Crouching, Ballista moved to the stairwell in the roof of the tower, and down the stairs. He walked the few paces to the northern of his two mines. Castricius was waiting just inside. Ballista waved his entourage in first: Maximus, Demetrius, the North African scribe, two messengers and a couple of equites singulares.
'We can talk here.' Ballista sat down. Castricius squatted down next to him, Demetrius near by. Ballista noted the solid-looking lintel, the thick pit props. It was not too bad here, just near the entrance. The oppression of the enclosed space could not overwhelm him when it was but three or four steps from the open air.
On the other side of the mine a line of men passed baskets of spoil from hand to hand out of the tunnel.
Castricius produced several scraps of papyrus, all covered in his scrawled writing. He expounded with admirable clarity and brevity the course of his tunnel. It was under the wall, under the outer glacis, and was scrabbling like a mole towards the Persian siege ramp. Consulting one piece of papyrus after another, he outlined his projected needs for pit props and slats to hold up the sides and roof, lamps and torches to light the work, and various incendiaries and their containers for the ultimate purpose of the mine. As Ballista approved the figures, Demetrius wrote them down.
Castricius went to check on progress; Ballista sat in silence where he was. A Sassanid missile thundered into the wall above. A fine shower of earth fell from the roof. Ballista, from wondering if the opposite pit prop was slightly off centre, found himself thinking about Castricius and his changes of fortune. He must have committed a terrible crime to have been sent to the mines. He had survived that hell, which spoke of uncommon resilience; he had joined the army (was there a regulation that should have prevented that?); finding the corpse of Scribonius Mucianus had brought his knowledge of mines to the attention of his Dux; being one of the three survivors of the ill-fated expedition of the young optio Prosper had won him the post of standard-bearer to Ballista. Now, for a second time, his experience of the mines had aided him, bringing promotion to acting centurion to dig this tunnel.
Another stone hit the wall; more dust drifted down. From this mine and the mutability of fortune, Ballista's thoughts moved along unconsidered back roads to the question of treachery. Demetrius had not been able to unravel its secrets, but the mere existence of the coded message attached to the arrow showed that there was still at least one traitor in the city of Aretc – or, at least that the Persians thought there was still a traitor active in the town. Ballista was sure they were right.
What did he know about the traitor? Almost certainly, he had murdered Scribonius Mucianus. He had burnt the artillery magazine. He had tried to organize the burning of the granaries. He was in communication, albeit sometimes interrupted, with the Sassanids. Clearly the traitor wanted the city to fall. Who could want such a thing, such a very monstrous thing? Could it be one of the townsmen, one of those who had lost their homes, family tombs, temples, slaves and all the liberties that were most precious to them because of the defensive measures Ballista had put in place? And hadn't he played his own part? How far could one go before destroying the very thing one was trying to protect?
If it was one of the townsmen, it was a rich one. Naptha cost a lot of money; it stank: only the rich could afford it, and the luxury of space to conceal its noxious smell. If the traitor was a townsman, it had to be one of the elite, one of the caravan protectors – Anamu, Ogelos, even Iarhai – or one of the other town councillors, like that ever-smiling Christian Theodotus.
But was it a townsman? What of the military? Ballista was very aware that Maximus still mistrusted Turpio. Not without reason. The humorous-faced Turpio had a past of proven duplicity. He had done well out of the death of his commander, Scribonius Mucianus. Despite Maximus's urgings, Ballista had never pressed the matter of what it was that Scribonius had used to blackmail Turpio. Maybe he would say one day, but Ballista very much doubted that Turpio could be forced to tell. On the other hand, Turpio had done well throughout the siege. His raid into the heart of the Persian camp had called for exceptional courage: one might say that he had earned the right to be trusted. But yet again, as Maximus had reminded him, courage is useful for a traitor – and so is being trusted.
Then there was Acilius Glabrio. Ballista knew that he was prejudiced against him, extremely prejudiced against the tribunus laticlavius. The crimped hair and beard, the supercilious manner: the northerner disliked almost everything about him. He knew that the young patrician detested serving under a barbarian. If Turpio was the traitor, it would be for money or to prevent his ultimate exposure as the killer of Scribonius – so money again. But if Acilius Glabrio proved to be the traitor, it would be about dignitas, that untranslatable quality that gave a Roman patrician a reason to believe in his superiority, a reason to exist. Ballista wondered if serving under an eastern monarch would be better for the dignitas of a Roman patrician than the humiliation of obeying the orders of a northern barbarian. In a certain light, the easterner could be thought less of a barbarian than a savage from the northern forests like Ballista.
Although Castricius was now in charge of this mine, the watch was being maintained on the area of town where the arrow with the coded message had struck the unfortunate soldier – who had, of course, died a few days after the doctor had extracted the arrow. Four equites singulares, whom Ballista could ill spare, kept up a more or less discreet observation. So far it had yielded nothing of use. As was to be expected, both Acilius Glabrio and Turpio had been seen on their rounds. All three of the caravan protectors had properties in the area. The Christian church ofTheodotus had relocated there.
Castricius returned. Again he squatted down, and again they talked of timber and olive oil and pig fat, of distances and density and momentum.
'Thank you, Centurion, thank you very much.' At Ballista's words, Castricius swelled with pride. He stood up sharply, but he was too old a hand to crack his head on one of the beams. He saluted smartly.
Stepping outside was like stepping into an oven. The heat sucked the air out of Ballista's lungs. Everywhere were shifting clouds of dust. The northerner could taste it gritty in his mouth, feel it sifting down into his lungs. Like everyone else he had a persistent cough.
As they walked to the southern mine there was a cry from the wall of 'baby on the way.' Most of the party threw themselves to the ground; Ballista and Maximus remained on their feet. The others might interpret it as coolness in the face of danger, but the two men knew that this was not true. Both stared upwards, thinking that if the missile were heading their way, they might get just a glimpse of it and have a split second to hurl themselves out of the way.