The Nubian pyramids on Mount Barkal and in Meroe, far more numerous than those of Lower Egypt, have lost much of their interest since investigations have shown that the civilization of Egypt and the prototypes of monumental art did not descend from Nubia, as was at first supposed, but arose in the delta and advanced up the stream. Inscriptions prove these pyramids to be some three thousand years younger than those of Memphis, dating them at as recent an epoch as the beginning of the Christian era. They are generally grouped in an extended necropolis, and differ from those of the ancient kingdom by a steeper angle of elevation, by a roundel-moulding upon the angles, and, above all, by much smaller dimensions. Though the truncated pyramidal form, as has been seen in a number of tombs at Gizeh, was not excluded from the funeral architecture of Egyptian subjects, it was never general. Rock-cut tombs were much more customary. The upright cliffs which border the banks of the Nile led naturally to such a formation, and in their sides are excavated caverns of very different dimensions, from the prevalent small, square chambers, with a narrow entrance high above the level of the valley, to the most extended series of rooms. These tombs were commonly decorated by mural paintings alone, but occasionally by carved architectural details, which always represent a wooden sheathing of slats or lattice-work. The larger chambers, even of the most primitive period, have the roof supported by square piers. [Illustration: Fig. 6.--Section of the Middle Pyramid of Abousere.] It is from these piers that the Egyptian columns seem to have originated, dividing from the outset into two classes and developing in different directions. One class of columns arose from chamfering the corners of the square pier, this support being thus transformed into an eight-sided, and, when the proceeding was repeated, to a sixteen-sided, shaft. The first phase of change, with its octagonal plan, was simple and advantageous--a predominance of vertical line was secured to the support, as well as greater room and ease of passage to the chamber. The second, the sixteen-sided figure, offered but few new advantages; on the contrary, the play of light and shade between the sixteen sides and angles was lost in proportion as the edges became more obtuse and less visible. As the sleek rotundity of an absolutely cylindrical shaft was not desirable, the blunt angles of the sixteen-sided prism, of rather coarse stone, were emphasized to avoid the disagreeable uncertainty which is felt when the plan is undecided between a polygon and a circle. This was effected by channelling the sides, making the arris more prominent and giving a more lively variation of vertical light and shade. The pier thus maintained, in some degree, its prismatic character while approaching the cylinder, and the channelled column arose. [Illustration: Fig. 7.--Transport of a Colossus. Egyptian Wall-painting.]