Perhaps of greater interest is the glimpse these excavations have afforded of a still more distant past. M. de Morgan found that the Citadel Hill has reached its present altitude of one hundred and twenty feet above the plain entirely by the accumulation of deposit left by successive generations of settlers. He sank a series of mines of considerable length into the side of the hill, and at various depths, down to 24·90 metres below the surface. The Achaemenian remains reach no farther down than 4·50 metres, and this stratum represents a period extending over 2,500 years. If we assume a similar rate of deposit for the remainder we arrive at more than B.C. 12,000 for the date of the lowest stratum examined. It is very remarkable that it was precisely at this depth, representing in any case an extremely remote period, that he found the most finished pottery, adorned with the most perfect artistic designs; and these, he has no doubt, could not have been produced except in a high state of civilisation.[234] There is some resemblance between these objects and others recently found in Egypt and ascribed to B.C. 6000.[235] This early civilisation seems to have been swept away by the invasion of a people in a much less advanced condition, who occupied the country for a long period of time;[236] it is not till these had disappeared and we ascend to a level of 12·95 metres below the surface that we come to the beginning of the Elamite deposit. It has a thickness of from eight to nine metres, which, according to our estimate, would require about five thousand years to form. It was in this stratum, between 4·50 and 12·95 metres below the surface that he made his principal discoveries. Here he came upon the walls of Elamite palaces and temples, which have enabled him to show that the method of decoration by means of enamelled brick of exquisite colour and design was extensively practised. The quantity of carbonised material leads to the conclusion that wood was largely employed in the construction of these edifices; and the remains of columns prove that the Persians derived their idea of columnar architecture direct from their predecessors. The inscriptions so recently found are still in the hands of Father Scheil, who is now engaged in the work of decipherment. They show, he says, the influence of Semitic speech in Elam at an early period, and the advocates of the antiquity of Semitic civilisation begin to hope they may still have occasion to rejoice.