Put upon the quest, a French scholar, M. de Sacy, born at Paris in 1758, copied some inscriptions of the Sassanid dynasty, which reigned in Persia A.D. 226-651. These were written in a known alphabet which is a mixture of Persian and Aramaic, called Pehlevi, and were shown by De Sacy to run in the following form:--"I, (M or W,) king of kings, son of (X,) king of kings, did thus and thus." Then, grouping together the several facts, came Dr. Georg Friedrich Grotefend, to formulate the theory that the Persepolitan inscriptions were written in three languages, and not three alphabets of one language, as Carsten Niebuhr had surmised. The recurrence of certain groups of characters led him to the inference that "the inscriptions were a fixed formula, only differing in the proper names." If these inscriptions began, like those read by De Sacy, with the formula, _X, the king of kings, son of D, the king of kings_, then it was clear that D was X's father; and, further, that D's father was not a king, because his name was not followed by that title, D being therefore the founder of a royal race. Now, Hystaspes, father of Darius, was not king, but satrap under Cambyses; and, joining his knowledge of history to his skill in philology, Grotefend found the key to the royal name. He lived for thirty years after this discovery, but added nothing to his triumph save "a fortunate guess of the name Nebuchadnezzar in one of the Assyrian inscriptions." Other decipherments followed; but it was reserved for the genius and industry of our countryman, the late Sir Henry Rawlinson, to discover the key whereby the ancient languages of Persia, Babylon, and Assyria can be read, and thus "a chapter of the world's history that had been well-nigh wholly lost made known to mankind." That eminent scholar in no wise exaggerated the importance of his work in claiming that its value in the interpretation of cuneiform writing is almost equal to that of the discovery of the Rosetta Stone in the interpretation of the hieroglyphic texts of Egypt (_Archæologia_, xxxiv. p. 75). [Illustration: Fig. 39.--Rock Inscription at Behistun]