Thief of Time - Sand

'And there is a second part to my plan,' said Wen.

'Ah,' said Clodpool, with an expression that he thought made him look wise, although in reality it made him look like someone remembering a painful bowel movement. 'A plan with a second part is always a good plan, master.'

'Find me sands of all colours, and a flat rock. I will show you a way to make the currents of time visible.'

'Oh, right.’

***

The Thief of Time - p66