Philo, who seems to be so well informed, tells us with what extreme care the casing was put in place. "The whole work," he says, "is so well adjusted, and so thoroughly polished, that the whole envelope seems but one block of stone."[218] The pyramid of Cheops has been entirely despoiled of its outer covering, and it is to that of Mycerinus that we must now turn if we wish to have some idea of the care with which the work was done. The lower part of this pyramid is still covered with long blocks of the finest granite, fixed and polished in the most perfect manner. At the foot of the Great Pyramid several blocks have been found which seem to have formed part of the casing of that edifice.[219] They are trapezoidal in form, and they show, as Letronne[220] long ago remarked, that the casing stones were placed one upon another, and adjusted by their external faces. They were not, as was at first supposed, sunk into the upper face of the course below by mortices which would correspond to the trench in the living rock in which the first course was fixed. As to whether the external faces of these blocks were dressed to the required angle before they left the quarry, or whether the work were done after they were in place we cannot say with any certainty, but it is most likely that the methods of proceeding changed with the progress of time and the succession of architects. In such a matter we should find, if we entered into details, diversity similar to that which we have already shown to have characterized the forms of the pyramids, their internal arrangements, and the materials of which they were composed. [218] Σύναρμον δὲ καὶ κατεξεσμένον τὸ πᾶν ἔργον, ὥστε δοκεῖν ὅλου τοῦ κατασκευάσματος μίαν εἶναι πέτρας συμφυίαν, p. 2,259, A. So, too, the elder Pliny, though with rather less precision: "Est autem saxo naturali elaborata et lubrica" (_Nat. Hist._ xxxvi. 12). [219] According to Jomard, the casing stones of the Great Pyramid were "a compact grey limestone, harder and more homogeneous than those of the body of the building" (_Description de l'Égypte_, t. v. p. 640); but according to Philo, this casing was formed, as we have already said, of various materials, so we need feel no surprise if blocks of granite or other rock are shown to have formed part of it. [220] _Journal des Savants_, August, 1841.