The British defeated the French in Egypt. In 1802 the Stone arrived at the British Museum and scholars attempted to decipher the hieroglyphs. By reading the Greek, it was clear that they outlined a series of honours bestowed upon the Pharaoh Ptolemy V in 196BC, but determining the phonetics of each symbol was problematic. If the Greek section mentioned a particular word, say, "honour", it was not obvious which hieroglyphs conveyed "honour". And even if appropriate hieroglyphs could be identified, the pronunciation remained unknown - a batch of hieroglyphs might mean "honour", but what was the ancient Egyptian word for "honour"?
In 1814, the English polymath Thomas Young had the insight to examine the cartouches, sequences of hieroglyphs enclosed in a loop (see below for Young's interpretation). The cartouches appeared several times on the Stone and Young took a guess that they represented the name Ptolemaios (Ptolemy). This name would be pronounced the same in any language, and so he simply applied a phonetic value to each hieroglyph.
Young had more or less correctly identified the phonetic values of seven hieroglyphs, which should have inspired him, but instead he abandoned his work. He believed that hieroglyphs did not usually represent sounds, but whole ideas, and that hieroglyphs were not phonograms, but semagrams. He excused his decipherment of Ptolemy on the grounds that he was descended from Lagus, a general of Alexander the Great, and a foreign name would have to be spelt out phonetically as there would not be an appropriate semagram within the hieroglyphic lexicon. He noted that Chinese writing, which uses semagrams, sometimes employs its characters phonetically to spell out foreign names.
It was not until 1822 that Jean-Francois Champollion, a young French linguist, continued Young's work. He was convinced that phonetics was the "soul" of all hieroglyphic inscription, not just used for foreign names, and achieved a complete understanding of the writing. This year is the bicentenary of the Rosetta Stone's discovery, and the story of Young and Champollion is featured in "Cracking Codes", which opens at the British Museum next Saturday.