Beyond the coal face

An original fiction passage set in the nineteenth century.

When the final basket had been hauled to the surface, Silas stayed below to lock the powder chest. As he lifted his lamp, a noise touched the new wall of coal: one light tap, followed by a dragging whisper. He looked towards the winding chain, but every link was still.

“Timber settling,” said Mr Rusk, though he had come back down the passage to listen. The two men waited. Water ticked from the roof into a pail, regular as a clock. Between the sixth drop and the seventh came another tap.

Silas pressed his knuckles against the coal. He knocked twice. Nothing answered. Mr Rusk laughed, too loudly, and turned towards the ladder. Then two knocks travelled back through the wall, separated by precisely the pause Silas had used. Dust loosened above them. It might have been the roof shifting; yet, as the lamp flame shrank, Silas thought the whole black face of the mine had drawn breath.

Analyse how the writer’s use of language and structure makes the source of the sounds uncertain. Support your answer with references to the passage.