The bronze relic was still in its case. The Greek text inscribed upon the ancient artefact stood out around its edge. Somewhere in the words was hidden the spring’s location. She could find it, she was sure, just as she had found other wonders of the past.
If she made a deal with the devil…
‘Okay,’ she said, looking back at Kroll. ‘You want me to help you locate the spring? I’ll do it — if you promise you’ll keep your word about letting us go.’
‘I promise,’ he replied.
Insincerity was almost painted on his face. But Nina had expected nothing else, and masked her suspicions. ‘All right. Then let’s get started.’ Macy gaped at her, appalled.
‘We already have maps and reference material,’ said Kroll. He gestured towards the door. One of the guards opened it, signalling for the prisoners to follow him down the hall.
‘What are you doing?’ Macy hissed to Nina as the group exited. ‘You actually want to help these people? They’re Nazis!’
‘Just go along with it,’ Nina whispered back.
Macy looked first confused, then conflicted. ‘Wait, you’ve got a plan?’
‘I hope so…’
Further furtive discussion was cut off as they were brought into a large room. One wall was occupied by a chalkboard, smudged remnants of German visible upon it. Several maps were pinned up; Nina recognised one as a street plan of Alexandria, the others showing the Middle East at various scales.
Kroll stood before the chalkboard, the still scowling Rasche alongside him. ‘Now, Dr Wilde,’ he said as the artefact was removed from its case, ‘begin.’
Nina exchanged looks with Macy and Banna, then regarded the metal fish. ‘Okay, based on what we learned when we examined it in Egypt, the first thing we need is a gnomon. How tall did it say it had to be?’
Banna read the text. ‘One dichas.’
‘Which if I remember my ancient Greek measurements was just over six inches, so fifteen-point-four centimetres.’ Kroll appeared surprised by her natural talent for mental arithmetic; clearly his research had not uncovered everything about her. ‘Okay, we need a stick exactly one hundred fifty-four millimetres tall that’ll stand up vertically in this hole.’ She tapped the fish’s eye.
‘I will have one made.’ The Nazi issued orders, one of his men hurrying out. ‘What else must be done?’
Banna kept reading. ‘We are supposed to enter the date using the large dials, then take a reading of the angle of the sun at noon outside Alexander’s tomb.’
‘Just like Eratosthenes,’ said Nina. The first person to make an accurate calculation of the earth’s circumference had done so by measuring the sun’s highest position in the sky over Egypt using the shadow cast by a gnomon. ‘Too bad you didn’t know that when we were actually in Alexandria,’ she said to Kroll. ‘It would have saved you the cost of a flight back there.’
The obese German was not amused. ‘The sun’s position can be calculated using computers.’
‘I know. The IHA has a good app.’
‘Which you will not be using. If you log into the IHA, they will know you are alive — and where you are. I am not a fool, Dr Wilde.’
‘Just a fascist,’ she said under her breath. ‘Ubayy, what next?’
‘We move the pointer until it touches the shadow,’ said Banna. He turned the artefact over, rotating one of the dials. The little bronze marker protruding from the slot moved in synchronisation. ‘Then we turn this small wheel,’ he touched it, ‘which locks part of the mechanism — it becomes a base for all other calculations.’
Nina read on. ‘Okay, then you follow Alexander’s route. Once you arrive in the Kingdom of Darkness, you dial in how many days it took you to get there from Alexandria…’ She straightened, impressed. ‘Wow, Andreas really was quite the gadget master. It adjusts the pointer’s position to take into account the sun’s precession. How much the sun moves up and down over time because of the earth’s axial tilt,’ she added, seeing varying degrees of incomprehension on the watching Nazis’ faces.
‘I know what it is!’ snapped Kroll. ‘Have you located the spring?’
‘Have you located the gnomon?’ she replied. ‘We can’t do anything until we can start taking measurements.’
The Nazi reddened with anger, while Rasche seemed amused that his superior had been made to look foolish. Kroll shouted more orders. Another man rushed out, coming back with the laptop from the study. A couple of minutes later, the first soldier returned, bearing a dowel. Kroll snatched it from him and thrust it at Nina.
The length of wood fitted neatly into the fish’s eye. ‘Okay,’ Nina said, ‘now we’ll need a protractor, a long ruler — and a website that can tell us the sun’s angle in a specific location on a specific day.’
The required tools were quickly procured. Nina held the protractor against the artefact. ‘Find the longitude and latitude of Alexander’s tomb. Then use them to calculate the sun’s position at noon.’ As Kroll began to search for the results on the computer, she took a closer look at the parts of the mechanism visible through the slot. ‘You know…’
‘What is it?’ Macy asked.
‘I just realised that we can work out the spring’s latitude right away! Based on Alexander’s historical route and what’s written in the Romance, it’s most likely somewhere in northern Iran. Which,’ she regarded one of the maps of the Middle East, ‘was a long trek in Alexander’s day — weeks, or even months — but today, you could fly there in a couple of hours. So if we don’t advance the date dial at all, the same result is still valid…’ She faced Banna. ‘How do you find out if you’re at the spring?’
The Egyptian rechecked the Greek text. ‘Once you reach the Kingdom of Darkness, you enter the number of days you have travelled, then take another reading of the sun at noon.’ He indicated the series of small notches inscribed along the slot’s edge. ‘Wherever the pointer is, if the shadow of the gnomon falls exactly five marks from it, then you are the correct distance north of the tomb. You then search for landmarks; the spring is in the shadow of a mountain peak, through the arch of Alexander.’
‘On the north face, I guess that means,’ said Macy. ‘If the sun’s behind it at noon.’
‘So if the travel time between the tomb and the spring is less than one day,’ Nina said, almost to herself as calculations took on form in her mind, ‘five of these marks must be equal to however many degrees of latitude there are between the two places. Right?’
Macy blinked. ‘Ah… if you say so.’
‘They are. Trust me. Five ticks represent how many degrees north you have to go from Alexandria.’ She glanced back towards Kroll. ‘Have you got those figures yet?’
The SS commander was displeased at being on the receiving end of a demand, but he continued to tap on the keyboard until he had a result. ‘Alexander’s tomb is at approximately thirty-one degrees and eleven minutes north, twenty-nine degrees and fifty-three minutes east.’
‘Okay, enter that into the solar altitude calculator. Set the date for tomorrow, and get the figure for twelve noon, local time.’
Still bristling, Kroll did so. ‘The sun’s position at midday is eighty-three-point-five degrees above the horizon.’
‘Eighty-three-point-five,’ Nina echoed. She used the protractor and ruler to find where the tip of a shadow cast by the gnomon would fall along the slot if the sun were at that height. ‘Okay, now we need to work out where the sun would be five ticks from that.’
‘The sun covers half a degree of arc,’ Banna pointed out. ‘We should take several measurements and find the average.’
‘Good point, but let’s just get the basics for now.’
Macy leaned closer, lowering her voice to the limit of audibility. ‘Slow it down, Nina! You’re leading these jerks right to it.’