seem to counterpoise and sustain each other in a fashion which is impossible in the case of the tetrahedron.
The one characteristic possessed in common by those relics of the Ancient Empire which we call pyramids, is their four-sidedness. To an attentive observer these buildings offer more diversities than would at first sight be believed. From Meidoum in the south to Abou-Roash in the north is a distance of 43½ miles as the crow flies. Between these two points, which may
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Fig. 128.—Plan of the Pyramid of Cheops.
be called the northern and southern boundaries of the pyramid field, about one hundred have been discovered, sixty-seven of which have been examined by Lepsius. Now, in this whole number there are not two which resemble each other in all particulars, or which seem to be copies of one model. We do not refer only to their height, which differs in an extreme degree. The three large pyramids at Gizeh are 482, 454, and 218 feet
