The observations made by Lepsius in the Stepped Pyramid and in one at Abousir seem to prove that some pyramids were constructed in this manner. In both of those buildings all necessary precautions were taken to guard against the weaknesses of such a system. It is difficult to understand how separate slices of masonry, placed one upon the other in the fashion shown by the section which we have borrowed from Perring's work (Fig. 134), could have had sufficient adherence one to another. Lepsius made a breach in the southern face of this pyramid, and the examination which he was thus enabled to institute led him to suggest a rather more probable system of construction. Upon the external sloping face of each step he found two casing-walls, but these did not extend from the ground to the apex of the monument, they reached no higher than the single step, so that they found a true resisting base in the flat mass (see Fig. 143) upon which they rested. Moreover, the architect provided for the lateral tying of the different sections of his work, as Lepsius proves to us by a partial section of the pyramid of Abousir. Two walls of fine limestone blocks inclose a filling in of rubble, to which they are bound by perpend stones which penetrate its substance. This method of construction has its faults, but it is so rapid that its employment is not to be wondered at. [Illustration: FIG. 143.--Section of the Stepped Pyramid at Sakkarah; from Lepsius.[194]] [194] Fig. 5 of his paper, _Ueber den Bau der Pyramiden_. [Illustration: FIG. 144.--Construction of the Pyramid of Abousir in parallel layers; transverse section in perspective from the geometrical section of Lepsius.[195]] [195] Fig. 8 of his paper, _Ueber den Bau der Pyramiden_.