Riptide

'Now I'm sure I don't understand,' Hatch said.

'I'm talking about an intersection of fault planes right under the island. Planes that got pulled apart somehow.'

'So there were underground cavities all along?'

Rankin nodded. 'Lots. Open cracks and fractures running every which way. Our friend Macallan merely widened and added as needed. But the question I'm still struggling with is, why are they here, under this island only? Normally, you'd see that kind of displacement on a wider scale. But here it seems restricted to Ragged Island.'

Their talk was interrupted as Neidelman stepped into the hut, He looked at each of them in turn, a smile flicking across his face, then vanishing again. 'Well, Malin, did Sandra give you the permission chit?'

'She did, thanks,' Hatch replied.

Neidelman turned toward Rankin. 'Don't stop on my account.'

'I was just helping St. John here with the 3-D model,' Rankin said.

Hatch looked from one to the other. The easygoing geologist suddenly seemed formal, on edge. Has something happened between these two? he wondered. Then he realized it was something in the way Neidelman was looking at them. He, too, felt an almost irresistible urge to stammer out excuses, explanations for what they were doing.

'I see,' Neidelman said. 'In that case, I have good news for you. The final set of measurements has been entered into the network.'

'Great,' Rankin said, and tapped a few more keys. 'Got it. I'm integrating now.'

As Hatch watched the screen, he saw small line segments being added to the diagram with blinding speed. In a second or two, the download was complete. The image looked much the same, though even more densely woven than before.

St. John, looking over the geologist's shoulder, sighed deeply. Rankin hit a few keys and the model began spinning slowly on its vertical axis once again.

'Take out all but the very earliest structures,' St. John said.

Rankin tapped a few keys and countless tiny lines disappeared from the image on the screen. Now, Hatch could see just a depiction of the central Pit itself.

'So the water traps were added toward the end,' Neidelman said. 'Nothing we didn't already know.'

'See any design elements common to Macallan's other structures?' Rankin asked. 'Or anything that might be a trap?'

St. John shook his head. 'Remove everything but the wooden beams, please.' Some more tapping and a strangely skeletal image appeared against the blackness of the screen.

The historian sucked in his breath with a sudden hiss.

'What is it?' Neidelman asked quickly.

There was a pause. Then St. John shook his head. 'I don't know.' He pointed to two places on the screen where several lines intersected. 'There's something familiar about those joints, but I'm not sure what.'

They stood a moment, a silent semicircle, gazing at the screen.

'Perhaps this is a pointless exercise,' St. John went on. 'I mean, what kind of parallels can we really hope to find to Macallan's other structures? What buildings are ten feet across and a hundred forty plus feet tall?'

'The leaning tower of Pisa?' Hatch suggested.

'Just a minute!' St. John interrupted sharply. He peered more closely at the screen. 'Look at the symmetrical lines on the left, there, and there. And look at those curved areas, one below the other. If I didn't know better, I'd say they were transverse arches.' He turned toward Neidelman. 'Did you know the Pit narrowed at the halfway point?'

The Captain nodded. 'From twelve feet across to about nine at the seventy-foot level.'

The historian began to trace points of contact across the wireframe model with his finger. 'Yes,' he whispered. 'That would be the end of an upside-down column. And that would be the base of an interior buttress. And this arch, here, would concentrate mass distribution at one point. The opposite of a normal arch.'

'Would you mind telling us what you're talking about?' Neidelman said. His voice was calm, but Hatch could see sharp interest kindling in his eyes.

St. John took a step away from the monitor, his face full of wonder. 'It makes perfect sense. Deep and narrow like that. . . and Macallan was a religious architect, after all...' His voice trailed off.

'What, man?' Neidelman hissed.

St. John turned his large calf eyes to Rankin. 'Rotate the Y-axis 180 degrees.'

Rankin obliged, and the diagram on the screen rotated into an upside-down position. Now the outline of the Water Pit stood upright, frozen on the screen, a glowing red skeleton of lines.

Suddenly there was a sharp intake of breath from the Captain.

'My God,' he breathed. 'It's a cathedral.'

The historian nodded, a triumphant smile on his face. 'Macallan designed what he knew best. The Water Pit is nothing but a spire. A bloody upside-down cathedral spire.'