These and similar questions of the highest importance for the early history of the Aryan language and mythology, however, must await their final decision, until the whole of the Veda and the Avesta shall have been published. Of this Burnouf was fully aware, and this was the reason why he postponed the publication of his researches into the antiquities of the Iranian nation. The same conviction is shared by Westergaard and Spiegel, who are each engaged in an edition of the Avesta, and who, though they differ on many points, agree in considering the Veda as the safest key to an understanding of the Avesta. Professor Roth, of Tübingen, has well expressed the mutual relation of the Veda and Zend-Avesta under the following simile: 'The Veda,' he writes, 'and the Zend-Avesta are two rivers flowing from one fountain-head: the stream of the Veda is the fuller and purer, and has remained truer to its original character; that of the Zend-Avesta has been in various ways polluted, has altered its course, and cannot, with certainty, be traced back to its source.' As to the language of the Achæmenians, presented to us in the Persian text of the cuneiform inscriptions, there was no room for doubt, as soon as it became legible at all, that it was the same tongue as that of the Avesta, only in a second stage of its continuous growth. The process of deciphering these bundles of arrows by means of Zend and Sanskrit has been very much like deciphering an Italian inscription without a knowledge of Italian, simply by means of classical and mediæval Latin. It would have been impossible, even with the quick perception and patient combination of a Grotefend, to read more than the proper names and a few titles on the walls of the Persian palaces, without the aid of Zend and Sanskrit; and it seems almost providential, as Lassen remarked, that these inscriptions, which at any previous period would have been, in the eyes of either classical or oriental scholars, nothing but a quaint conglomerate of nails, wedges, or arrows, should have been rescued from the dust of centuries at the very moment when the discovery and study of Sanskrit and Zend had enabled the scholars of Europe to grapple successfully with their difficulties.