The three great pyramids of Gizeh are the most remarkable and the best known of all those of Egypt. Of these the first, erected by Cheops, or, as he is now more correctly named, Khufu, is the largest; but the next, by Chephren (Khafra), his successor, is scarcely inferior in dimensions; the third, that of Mycerinus (Menkaura), is very much smaller, but excelled the two others in this, that it had a coating of beautiful red granite from Syene, while the other two were revêted only with the beautiful limestone of the country. Part of this coating still remains near the top of the second; and Colonel Vyse[29] was fortunate enough to discover some of the coping-stones of the Great Pyramid buried in the rubbish at its base. These are sufficient to indicate the nature and extent of the whole, and to show that it was commenced from the bottom and carried upwards; not at the top, as it has sometimes been thoughtlessly asserted.[30] [Illustration: No. 7. Section of Great Pyramid.] Since Colonel Vyse’s discovery, however, further casing-stones have been found in situ by Mr. Flinders Petrie, whose measurements, taken in 1880-82, and published in the following year,[31] are the most accurate yet made. The dimensions hitherto given have shown a difference of as much as eighteen inches in the length of the sides, which, if the pyramid had been set out on a perfectly clear level ground, would have detracted from the perfection which has been claimed for its setting out. This difference, however, it appears now, was due to the fact that the various observers had measured from angle to angle of the corner sockets, and had “assumed that the faces of the stones placed in them rose up vertically from the edge of the bottom until they reached the pavement (whatever level that might be), from which the sloping face started upwards.” This, however, was not the case; the sloping sides of the Pyramid continued down to the rock surface, and the base was eventually partially covered over by a level pavement or platform;[32] the parts covered over varying in extent according to the depth they were carried down. Mr. Petrie utilized the angle sockets for the purpose of obtaining the true diagonals of the casing, and having computed a square which passed through the points of casing found on each side, and having also its corners lying on the diagonals of the sockets, obtained the dimensions of the original base of the Great Pyramid casing on the artificial platform or pavement, which was as follows:— Sq. In. Ft. In. North side 9069·4 or 755 9·4 East side 9067·7 or 755 7·7 South side 9069·5 or 755 8·6 West side 9068·6 or 755 8·8 The mean being 755 ft. 8·8 in., and the extreme difference being 1·7 of an inch only. The actual height of the Great Pyramid from level of platform was 481 ft. 4 in., and the angle of casing 51° 52ʺ.