Grotefend's key to the reading of that style of cuneiform writing which invariably occupied the first place when the three styles were ranged one under the other, or occupied the most prominent place when a different arrangement was adopted, met with universal acceptance.

He determined that the language of the style which, for the sake of convenience, we may designate as No.

1, was Old Persian,--the language spoken by the rulers, who, it was known through tradition and notices in classical writers, had erected the series of edifices at Persepolis, one of the capitols of the Old Persian or, as it is also called, the Achaemenian empire.

By the year 1840 the decipherment of these Achaemenian inscriptions was practically complete, the inscriptions had been read, the alphabet was definitely settled, and the grammar, in all but minor points, known.

It was possible, therefore, in approaching the Mesopotamian style of cuneiform, which, as occupying the third place, may be designated as No.