Far away in the clouds, it seemed, they could hear a faint humming, some new sound, something mechanical in its regular beating, yet with clamorous throatiness of some human force cleaving its way through the resistless air.

With every second it grew louder.

The men stood clutching one another.
"Have you got the fuse ready?
They must hear it in a moment." Granet muttered.
Collins assented silently.

The reverberations became louder and louder.
Soon the air was full of echoes.

From far away inland dogs were barking, from a farm somewhere the other side of the road they heard the shout of a single voice.
"Now," Granet whispered.
Collins leaned forward.