The savants of the seventeenth century were not "wiser in their generation" than the rude nomads who pitched their tents under the shadow of the stone monsters. Many years after Della Valle's visit the Oriental scholar, Hyde, in a book on the Ancient Persian Religion, soberly suggested that the signs were designed by some fantastic architect to show into how many combinations the same kind of stroke would enter. It is a wonder that he did not, with equal sobriety, suggest that they were related to the well-known Norman "hatchet-work." And so the guessing went on. One antiquary contended that they were talismanic signs; another that they were mystic formulæ of the priests, or astrological symbols of the old Chaldean star-worshippers; another saw in them a species of revealed digital language wherewith the Creator talked to Adam, whence the primitive speech of mankind was derived; while others conjectured them to be Chinese, or Samaritan, or Runic, or Ogam characters. Most fantastic of all, one ingenious theorist saw in them the action of numberless generations of worms! But by the middle of the eighteenth century a sane school of investigators had found its leader. A great traveller, Carsten Niebuhr, father of the famous historian of early Rome, was the first to divine the true character of the inscriptions. He agreed with Della Valle that they were written from left to right, and he saw that they were made up of three different sets of characters, each meaning the same thing. But beyond showing, in his careful transcript published in 1764, that one of the three scripts was simpler in character than the others--all, as he assumed, being alphabetic varieties of one language--he could not go. The meaning still remained a mystery. Thirty years later, Münter, a Danish philologist, correctly guessed that the diagonal bar [Symbol], which occurred frequently, was a sign for the separation of words, and, next, he discovered the vowel signs, which, as distinct characters, are absent from the Hebrew and other Semitic languages. This was a great step towards final decipherment. Herodotus (i. 125, &c.) speaks of the Achæmenid dynasty of Persian kings who were the lords of Asia in the sixth and fifth centuries B.C. The ruins of Persepolis are identified as the remains of their palaces. Of this royal house the famous Darius was a member, and Herodotus tells how that monarch, "having gazed upon the Bosphorus, set up two pillars by it of white stone with characters cut upon them, on the one Assyrian and on the other Hellenic, being the names of all the nations which he was leading with him" (iv. 87). The engraving of the same inscription in two or more different languages (of course necessitated by making their decrees known to the various peoples whom they ruled) was thus shown to be a custom of the Persian kings.