The name of Jean-Francois Champollion (1790-1832) will always be associated with the decipherment of Egyptian hieroglyphs. Champollion himself was a child prodigy who had taught himself numerous ancient languages in his teenage years, despite not having received any formal education. In this 1824 work, he expands on the discoveries he had previously outlined in 1822, giving a long and systematic account of his research, which was based on the insight of Thomas Young that clusters of hieroglyphs on the tri-lingual Rosetta Stone could be matched to known Greek and Latin names. He gave phonetic values to the signs, and then linked them to the Coptic language (familiar from its use in the liturgy of the Coptic Christian Church in Egypt), which he recognised as being descended from ancient Egyptian. The work was originally published in two volumes (the second being of illustrations), which are here bound as one.