Hamadan inscription upon which his work was chiefly founded. But there was another to which he made frequent reference, especially towards the close of his Memoir. This is the I inscription of Niebuhr, which is copied from the outside wall, on the southern side of the great platform of Persepolis.[391] It will be recollected that Grotefend had called attention to this inscription in 1832, and had pointed out that it evidently contained a long list of proper names.[392] Whether this suggestion ever reached Burnouf it is impossible to say, but it is certain he made it an early object of study; and from it he derived the cuneiform sign ‘B,’ with which he signed his letters to Lassen. The method he pursued to determine the value of an unknown sign was to collect all the words in which it occurred, and endeavour to assign to it a letter, from among those not already rigorously determined, that would produce a word for which some meaning might be found by comparing it with Zend. For example, the word with which the Darius at Hamadan begins consists of only two letters, which, according to Grotefend, would yield _vu_. But Burnouf could make no sense out of this, and he accordingly substituted a _b_ for the first letter (𐎲). The result was that he could not only extract a sense out of _bu_—which he compared with the Sanscrit _bhû_ and _bû_ ‘to be,’ but two or three other words were also rendered intelligible by the same change.[393] The consideration, however, that finally settled the matter was the discovery of a name in the I inscription, which, upon the supposition that the letter in question was a _b_ would yield ‘Bakhtroch,’ and this he had no difficulty in identifying with Bactria. Hence he altered the _v_ of Grotefend into a _b_ without apparently recognising that he merely restored the value originally given to that sign by Münter.[394]