"They are nothing more nor less than time-fuses." "Time-fuses!" Hillyard repeated.

"I don't understand." "Listen!" Marnier looked around.

There was no one near enough to overhear him, if he did not raise his voice; and he was careful to speak in a whisper.
"Two things." He ticked them off upon his fingers.

"First, hydrofluoric acid when brought into contact with certain forms of explosive will create a fire.

Second, hydrofluoric acid will bite its way through glass.