Flame Cannon

There are few weapons that can put fear into the heart of a foe like the Flame Cannon, one of the deadliest inventions of the Engineers Guild. A volatile concoction of hot oil and molten tar is mixed within the Flame Cannon before air is pumped into the barrel; soon the pressure inside is tremendous and the barrel is almost ready to burst. At precisely the right moment, the Dwarfs place a burning oily wad into the nozzle and release the pressure. The mixture catches fire as it whooshes from the barrel in a leaping spurt. The burning oil arcs into the air towards the enemy ranks and, with a bit of luck, lands in the middle of the foe, spraying boiling tar over them. For longer ranged shots, the Dwarfs simply apply more pressure, and the most experienced crew know exactly when to release the straining valves to achieve maximum distance. Those crew who misjudge this subtle balance rarely get another chance.

Enemies struck by Flame Cannons have their melted off them in a slough, leaving only scorched bones and a foul-smelling liquid that is best described as 'goo'. Even the bravest of those who survive, after seeing their comrades so gruesomely reduced, have been known to flee immediately.

Source

 * Armybook: Dwarfs (8th Edition) pg. 19