That muffled sound of quick firing came from metallic cartridges exploding within the cases that held them; each case would burst and set fire to others beside it; like the spark that runs along a fuse, the train of boxes would blow up in quick succession till the large stores of gunpowder were fired and then a mass of dynamite beyond.

There were divisions in the vaults, there were doors, there were walls, but Giovanni well knew that no such barriers would avail for more than a few minutes.
Without raising his voice, he led his companions to the open door, speaking as he went.
'The magazine will blow up in two or three minutes at the outside,' he said.

'Send the men running in all directions, and go yourselves, to warn the people in the cottages near by to get out of doors at once.
It will be like an earthquake; every house within five hundred yards will be shaken down.

Now run! Run for your lives and to save the lives of others! Call out the men as you pass the gates.' The three darted away across the open space that lay between the central building and the guard-house.

Giovanni ran, too, but not away from the danger.