From above the roof there came a sudden tearing sound, which at first he believed to be the wind.
It increased to a loud, confusing, swishing whistle, as though hundreds of sabres were being whirled in circles overhead.
Berkley rose, looking upward at the ceiling as the noise grew in volume like a torrent of water flowing over rocks.
Ailsa also had risen, laying one hand on his arm, listening intently.
"What is it ?" she breathed.
"It is the noise made by thousands of bullets streaming through the air above us.

It sounds like that in the rifle-pits.

Listen!" The strange, bewildering sound filled the room.

And now, as the wind shifted, the steady rattle of musketry became suddenly audible.

Another sound, sinister, ominous, broke on their ears, the clang of the seminary bell.
"Is it an attack on this place ?" she asked anxiously.