In the Second Pyramid, the bottom corner of casing (which was in granite) had a vertical base 10 or 12 in. high, against which the pavement was laid; and the following were the dimensions obtained:— Sq. In. Ft. In. North side 8471·9 or 705 11·9 East side 8475·2 or 706 3·2 South side 8476·9 or 706 4·9 West side 8475·5 or 706 3·5 The mean being 706 ft. 2·9 in., and the extreme difference in the length of side 5 in. The height was 472 ft., and the angle of casing 53° 10ʹ. The Third Pyramid was never quite finished, and there is some difficulty in determining the exact level of platform. The mean length of the sides was calculated by Mr. Petrie as 346 ft. 1·6 in., its height 215 ft., and the angle of its casing 51° 10ʹ. From this it will be seen that the area of the Great Pyramid (more than 13 acres) is more than twice the extent of that of St. Peter’s at Rome, or of any other building in the world.[33] Its height is equal to the highest spire of any cathedral in Europe; for, though it has been attempted to erect higher buildings, in no instance has this yet been successfully achieved. Even the Third Pyramid covers more ground than any Gothic cathedral, and the mass of materials it contains far surpasses that of any erection we possess in Europe. All the pyramids (with one exception) face exactly north, and have their entrance on that side—a circumstance the more remarkable, as the later builders of Thebes appear to have had no notion of orientation, but to have placed their buildings and tombs so as to avoid regularity, and facing in every conceivable direction. Instead of the entrances to the pyramids being level, they all slope downwards—generally at angles of about 26° to the horizon—a circumstance which has led to an infinity of speculation, as to whether they were not observatories, and meant for the observation of the pole-star, &c.[34] All these theories, however, have failed, for a variety of reasons it is needless now to discuss; but among others it may be mentioned that the angles are not the same in any two pyramids, though erected within a few years of one another, and in the twenty which were measured by Colonel Vyse they vary from 22° 35ʹ to 34° 5ʹ. The angle of the inclination of the side of the pyramid to the horizon is more constant, varying only from 51° 10ʹ to 52° 32ʹ, and in the Gizeh pyramid it would appear that the angle of the passage was intended to have been about one-half of this.