The Rosetta Stone
The Rosetta Stone was discovered in 1799 in a small Egyptian village in the Nile Delta. It was realized, almost at once, that the three distinct inscriptions were all the same story. The last of the three inscriptions was in Greek and could therefore be read in the 19th Century. Neither of the two Egyptian scripts, demotic and hieroglyphic, could be understood at that time.
The first steps in deciphering the Egyptian scripts were made by comparing the most frequent Greek words with a group of signs in the demotic script that occurred about the same number of times. The next step came because a cartouche (an elongated oval) was assumed to contain the symbols for a royal name. The name of Ptolemy was included in the Greek text on the Rosetta stone. Furthermore, the names of both Ptolemy and Cleopatra were presumed to be on another commemorative Greek and hieroglyphic inscription. Four letters are the same in each name.
These could then be equated to Egyptian symbols in the cartouche.
Starting with the symbols in the cartouche and comparing each new letter back to the Greek text, gradually the alphabet in both Egyptian scripts was deciphered.
The final step came when partially translated words from the hieroglyphic script were compared to the Coptic language.
Ancient Egyptian texts could now be understood. An enormous library of Egyptian texts could now be translated and interactions between the Hebrews and the Egyptians read from an Egyptian point of view. These could now be compared with Old Testament records.
Source: Carol Andrews, The Rosetta Stone, British Museum Publications 1981, 31 pp