Rosetta StoneFrom the Britannica Concise Encyclopedia:
Inscribed stone slab, now in the British Museum, that provided an important key to the decipherment of Egyptian hieroglyphs. An irregularly shaped block of black basalt with inscriptions in hieroglyphs, Demotic Egyptian, and Greek, it was discovered by Napoleon's troops near the town of Rosetta (Rashid), northeast of Alexandria, in 1799.