It was the same with the sepulchres of the kings. Each sovereign began the construction of his pyramid as soon as he found himself upon the throne. But, in case his life and his reign should be cut short, he began with those constituents of the tomb which were absolutely necessary. He pressed on the work until he had raised a pyramid of moderate size with its mummy chamber. When this point had been reached, his immediate anxiety came to an end; but that was no reason for interrupting the course of the work. The higher and wider his pyramid, the more efficient a guardian of his body would it be, and the more impressive would be the message carried down by it to posterity as to the power of its builder. Year after year, therefore, he employed crowds of impressed workmen to clothe it in layer after layer of dressed stone or brick, so that the edifice raised in comparative haste at the beginning of his reign, became in time nothing but the nucleus or kernel of one many times its size.[187] The construction was thus begun in the centre and was developed outwards, like the timber of a tree in successive years. As the pyramid grew in extent and height, each successive coat, so to speak, required more hands and more time. We have no reason to believe that each coat had to be finished within a certain period, and so it would be futile to attempt to found any calculation as to the duration of the different reigns upon the number of these concentric layers; but we may assert in a general way that the highest pyramids correspond to the longest reigns. We know, by the witness of ancient authors, that the kings who built the three great pyramids at Gizeh, namely, Cheops, Chephren, and Mycerinus, each reigned about sixty years. History thus confirms the truth of the induction which arises from the study of those monuments and from a comparison of the constructive processes made use of by the architects of the pyramids.[188] [187] This method of construction may be easily recognized in the Pyramid of Meidoum. That curious structure was built in concentric layers round a nucleus. These layers are by no means equal in the excellence either of the workmanship or of the materials employed. Some show supreme negligence; in others we find the builders of the Ancient Empire and their materials both at their best. The same fact has been observed in regard to the Stepped Pyramid and the pyramids at Abousir. It would seem that the work was assigned in sections to different _corvées_, whose consciences varied greatly in elasticity. (MARIETTE, _Voyage de la Haute-Égypte_, p. 45.) [188] LEPSIUS, _Briefe aus Ægypten_, pp. 41, 42 (in speaking of the Pyramid of Meidoum, from which he received the first hint of this explanation). See also his paper entitled _Ueber den Bau der Pyramiden_, in the _Monatsbericht_ of the Berlin Academy, 1843, pp. 177-203.