He is an excellent guide.'
'Better than Boris, at least,' Nicholas agreed, as he fished out his
barometer and took another reading.
'You look particularly pleased with yourself.' Royan watched his face as
he studied the instrument.
'Every reason to be,' he told her. 'Allowing one hundred and eighty feet
for the height of the cliff below us, and another fifty feet for the
depth of the pool, the entrance to the sink-hole is still over a hundred
feet higher than your outlet through the fern grotto on the other side
of the ridge.'
'Which means?'
'Which means that there is a distinct possibility that the streams are
one and the same. The inflow is here in Taita's pool and the outflow is
from your grotto.'
'How on earth did Taita do it?' she puzzled. 'How did he get to the
bottom of the pool? You are the engineering marvel. Tell me how you
would do it.'
He shrugged, but she persisted. 'I mean, there must be some established
way of doing things like that, of working under water. How do they build
the piers of a bridge, or the foundations of a dam, or - or - or how did
Taita himself build the shaft below the level of the Nile to measure the
flow of the river? You remember the description that he gives of his
hydrograph in River God?'
'The accepted technique is to build a coffer dam ' Nicholas said
casually, and then broke off and stared at her. 'My oath, you really are
a corker. A dam! What if that old ruffian, Taita, dammed the whole
flipping river!'
'Would that have been possible?'
'I am beginning to believe that with Taita anything is possible. He
certainly had unlimited manpower at his disposal, and if he could build
the hydrograph on the Nile at Aswan, then he understood very clearly the
principles of hydrodynamics. After all, the old Egyptians' lives were
completely bound up with the seasonal inundations of the river and the
management of the floods. From what we have gathered about the old man,
it certainly seems Possible.'
'How could we prove it?'
'By finding the remains of his dam. It had to be a hell of a work to
hold the Dandera river. There is a good chance that some evidence of it
remains.'
'Where would he have built the dam?' she asked excitedly. 'Or let me put
it another way, where would you site the dam if you had to do it?,
'There is one natural place for it,' he answered promptly. 'The spot
where the trail leaves the river and detours down the valley, and the
river falls into the chasm.
They both turned their heads in unison and looked upstream.
'What are we waiting for?' she asked, and sprang to her feet. 'Let's go
look-see!
Their excitement was infectious, and Tamre giggled and danced ahead of
them along the trail through the thorns and then up the valley to the
point where it rejoined the river. The sun had lost the worst of its
