Sentence:  And one day fortune played into his hand by sending a customer to the shop for two ounces of gunpowder, when Paul was standing by. / "Do you keep gunpowder, then?" said Paul, with kindling eyes, as the man left the shop. / "Yes," answered his brother innocently, "but we only sell it to grown-up people. Boys wouldn't know what to do with it." / "Wouldn't they, though? Why, you can make <WSD>fizgigs</WSD> of it that blaze like Vesuvius, the burning mountain." 
Meaning of the word marked with <WSD> tags:  A small squib-like firework that explodes with a fizzing or hissing noise.