" Vimes, listening with his mouth open, wondered why the hell it was that dwarfs believed that they had no religion and no priests. Being a dwarf was a religion. People went into the dark for the good of the clan, and heard things, and were changed, and came back to tell…And then, fifty years ago, a dwarf tinkering in Ankh-Morpork had found that if you put a simple fine mesh over your lantern flame it'd burn blue in the presence of the gas but wouldn't explode. It was a discovery of immense value to the good of dwarfkind and, as so often happens with such discoveries, almost immediately led to a war." And afterwards there were two kinds of dwarf," said Cheery sadly. " There's the Copperheads, who all use the lamp and the patent gas exploder, and the Schmaltzbergers, who stick to the old ways. Of course we're all dwarfs," she said, " but relations are strained. "