in Geometry, is a solid standing upon a triangular, a square, or a polygonal basis, and terminating in a point at the vertex; or it is a solid figure, consisting of several triangles, the bases of which are all in the same plane, and have one common vertex.

Pyramid is also applied to a colossal structure, corresponding in form to the geometrical definition of the solid, and remarkable not only for its magnitude and antiquity, but likewise for the mystery which still overshadows the object contemplated in its construction.

The number of pyramids scattered over Egypt, Nubia, and Ethiopia or Meroë, is very great indeed; but by far the most remarkable are those of Djizeh, Sakharra, and Dashour, on a plain to the north of Cairo, in Egypt. The first of these places, which is situated on the western bank of the Nile, and nearly in the latitude of Cairo, is distinguished above the others by possessing the three principal pyramids mentioned by Herodotus, and still justly numbered amongst the wonders of human art.

The largest of these pyramids, which goes by the name of Cheops (a Greek corruption of the Egyptian Khéops or Copt), stands on an elevation upwards of 150 feet above the subjacent plains, and rises to an altitude above the base of about 498 English feet. It is ascended by an uninterrupted series of steps, diminishing from four feet to two and a half in height, as the structure narrows towards the vertex. The breadth of each step is equal to its height. Upon the top there is a platform thirty-two feet square, consisting of nine blocks of stone, wherein travellers of all ages and nations have inscribed their names in their respective languages. This pyramid was explored first by our country- Pyramid. Mr Davidson in 1763, and afterwards with still greater success by Captain Caviglia in 1817. A full account of the adventurous explorations of each will be found in the article Egypt, vol. viii. p. 547 et seq. of the present work. In all of the pyramids the entrances are in the north front, and the descending passages slope at an angle of twenty-six or twenty-seven degrees. This line seems to be nearly directed to the pole, and hence the northern face of the pyramid is almost in the plane of the earth's equator; a circumstance which goes far to show that the passages in question were intended for the purpose of astronomical observation.

The second pyramid, called that of Cephrenes, is stated by Denon to have a base 655 feet each side, and to be 398 feet in height. The pyramids are supposed to have been all coated or cased with stucco made of gypsum and flint; and in fact forty feet of coating still adhere to that of Cephrenes. But the great pyramid has no appearance of having been touched in this way; and on that of Cephrenes the coating was probably never completed, as no indications of it were discovered on removing the sand from its base. In 1816, Belzoni discovered the entrance in the north front of the second pyramid. Advancing along a narrow passage, he found that it terminated in a chamber at the centre of the pyramid, cut out of the solid rock, the dimensions of which he ascertained to be forty-six feet in length, sixteen in breadth, and nearly twenty-four feet in height. This chamber contained a sarcophagus of the finest granite, half sunk in the floor, with the lid drawn to one side and broken, and within were bones, supposed to be those of a bull, mixed with rubbish. An Arabic inscription on the wall proved that it had been explored by the curious of a former age. The dimensions of the pyramid were ascertained to be, the base 684 feet each side, the perpendicular height 456 feet, and the coating from the top to where it terminates 140 feet. (See the article Egypt, ubi supra.)

The third pyramid, situated beyond that of Cephrenes, and called by the name of Mycerinus, appears to have been cased with granite, at least fragments of that material were found amongst the rubbish. But it still remains to be opened by some future traveller, Belzoni, with all his enterprise, having failed in the attempt. It is only 280 feet at the base, and 162 in height; and beyond it there is another of still smaller dimensions, having its summit crowned by one large block of stone, as if for a pedestal. The stability of these enormous piles was increased by the stones having been so fixed as to slope inwards, and the perfection of the adjustment may be inferred from this, that not one of them has yet swerved from its position. The structures raised by the ancient Egyptians were intended to last for ever.

The pyramids of Sakhara are three miles south of those of Djizeh, and the pyramids of Dashour are beyond those of Sakhara, whilst more of brick or of stone are scattered over the plain, intermixed with the excavations, cemeteries, and fragments of statues or edifices, which mark out the site of the second capital of the Pharaohs. Some of them are rounded at the top, and resemble hillocks cased with stone. One has steps like that of Cheops, the ranges, six in number, being twenty-five feet in height and eleven feet in width; and the total height is 150 feet. There is another, built also with steps or ranges, and not much inferior in altitude to that of Cheops. The stones of these pyramids are much decayed, and gradually crumbling into dust, evidently from great age. One of them is built of unburned bricks, containing shells, gravel, and chopped straw, and is altogether in a very mouldering state.

For some notices of the various opinions stated by travelers as to the purposes for which these extraordinary structures are supposed to have been intended, the reader is again referred to the article Egypt in this work. The bones found in the chamber of the pyramid of Cephrenes, not to mention other circumstances, seem to have some connection with the worship of the sacred bull Apis; and besides, from the care with which the entrances appear to have been concealed, it is not impossible that there may yet be many undiscovered chambers, both in the pyramid of Cheops and in that of Cephrenes. It is very remarkable, too, that not a single sculpture or hieroglyph has been discovered in any pyramid which modern enterprise and research have yet explored.