The fundamental motive of the pyramid is the funeral mound. A small upheaval above the natural level of the ground results of itself from the earth displaced by the bulk of the buried body. Our present practice of interment clearly illustrates this. Increased dimensions elevate the mound to an independent monument. Many nations, some of a high degree of civilization, have contented themselves with such imposing hills of earth over the grave,--tumuli, which, from the manner of their construction, assumed a conical form. Others placed the mound upon a low cylinder, thus better marking its distinction from accidental natural elevations. The Egyptians and the Mesopotamians rejected the cone entirely, and formed, with plane surfaces upon a square plan, the highly monumental pyramid. Peculiar to the former people are the inclined sides which give to the pyramid its absolute geometrical form, as opposed to the terraced structures of Chaldæa. The sand of the desert ebbed and flowed fifty centuries ago as constantly as in our time, when the sphinx, after being uncovered to its base, has been quickly hidden again to the neck. Rulers, unwilling that their gigantic tombs should be thus submerged, were obliged to secure to them great height, with inclined and unbroken sides, upon which the sand could not lodge. The typical pyramid of Gizeh, near Cairo--the monument of Cheops (Shofo, Suphis), the first or second king of the fourth dynasty--rises above the broad necropolis of Memphis, by far the largest and one of the most marvellous works of mankind. (_Fig._ 1.) With a ground-line mean of 232.56 m., the great pyramid attained an altitude of 148.21 m., of which the entire apex is now overthrown, leaving a height of about 138 m.[A] The original intention of the builders was doubtless an absolutely square plan. The greatest difference in the length of the ground-lines of the base is 0.45 m. The angle of the upward inclination of the sides has been found, by measurements at various points, to average 51° 51´ 43´´. The entire pyramid is solidly built of massive blocks, pierced by a few narrow passages which lead to small chambers. (_Fig._ 2.) Like most of these monuments, the entrance is situated somewhat above the ground; it opens to a passage which descends with a gentle inclination. The shaft is covered with stones leaning against each other, so as to present the great resistance of a gable to the superimposed mass. In passing out of the masonry it is continued into the natural rock under the same angle, 26° 27´. Near the point of separation it meets with another passage, which ascends with an inclination of 26° 6´ to the centre of the structure, sending off a nearly horizontal branch at half-way. All three shafts lead to grave-chambers, the highest being the most important. As the ascent continues above the horizontal branch, its importance is emphasized by the passage being increased from 1.2 or 1.5 m. high to a corridor 8.5 m.