It was the greatest puzzle in the world. For three thousand years the ancient Egyptians covered the walls and ceilings of their temples and tombs with a form of writing known as hieroglyphs. More, the bone-dry climate of Egypt had preserved vast quantities of this hieroglyphic text written on papyrus. And in 1800, no one on earth could read a word of it. When Egypt became Christian in the fourth century A.D., the use of these hieroglyphs, associated with paganism, died out. The last known hieroglyphic inscription was chiseled into stone in the year 394. Within a generation, the last...