Greek inventor Archimedes is said to have used mirrors to burn ships of an attacking Roman fleet. But new research suggests he may have used steam cannons and fiery cannonballs instead.

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....