It was something like Arabian Nights magic, and something like being in church.

No one cared to speak.
It was Cyril who said at last-- 'Please we want to know where the other half of the charm is.' 'The part of the Amulet which is lost,' said the beautiful voice, 'was broken and ground into the dust of the shrine that held it.

It and the pin that joined the two halves are themselves dust, and the dust is scattered over many lands and sunk in many seas.' 'Oh, I say!' murmured Robert, and a blank silence fell.

'Then it's all up ?' said Cyril at last; 'it's no use our looking for a thing that's smashed into dust, and the dust scattered all over the place.' 'If you would find it,' said the voice, 'You must seek it where it still is, perfect as ever.' 'I don't understand,' said Cyril.
'In the Past you may find it,' said the voice.
'I wish we MAY find it,' said Cyril.
The Psammead whispered crossly, 'Don't you understand?
The thing existed in the Past.

If you were in the Past, too, you could find it.