A legend begun in the Medieval Ages tells of how Archimedes used mirrors to concentrate sunlight as a defensive weapon during the siege of Syracuse, then a Greek colony on the island of Sicily, from 214 to 212 B.C. No contemporary Roman or Greek accounts tell of such a mirror device, however.
Both engineering calculations and historical evidence support use of steam cannons as “much more reasonable than the use of burning mirrors,” said Cesare Rossi, a mechanical engineer at the University of Naples “Federico II,” in Naples, Italy, who along with colleagues analyzed evidence of both potential weapons.
The steam cannons could have fired hollow balls made of clay and filled with something similar to an incendiary chemical mixture known as Greek fire in order to set Roman ships ablaze. A heated cannon barrel would have converted barely more than a tenth of a cup of water (30 grams) into enough steam to hurl the projectiles.