But then finally a cart-train came down out of the north laden with charcoal and with firewood, and Vrej Esphahnian unveiled a wooden crate containing a gross of glass bottles (smoky brown, striated, and bubbly, but more or less transparent), and they were ready to go. Jack had mentioned to them, and Padraig had demonstrated beyond all question, that the apparatus would destroy itself in a spitting storm of white fire shortly after they were finished using it; they had, in other words, one and only one chance.