On this day in 1799, during Napoleon Bonaparte’s Egyptian campaign, a
French soldier discovers a black basalt slab inscribed with ancient writing
near the town of Rosetta, about 35 miles north of Alexandria. The irregularly
shaped stone contained fragments of passages written in 3 different scripts:
Greek, Egyptian hieroglyphics and Egyptian demotic. The ancient Greek on
the Rosetta Stone told archaeologists that it was inscribed by priests
honoring the king of Egypt, Ptolemy V, in the second century B.C. More
startlingly, the Greek passage announced that the three scripts were all of
identical meaning. The artifact thus held the key to solving the riddle of hieroglyphics, a written language that had been “dead” for nearly 2,000
years.

The Rosetta Stone on display in The British Museum.

"Lithograph image depicting a group of scholars inspecting the
Rosetta Stone during the Second International Congress of
Orientalists, 1874.