jeudi 25 février 2021

La construction des pyramides égyptiennes selon Leslie Grinsell - 4e partie : la superstructure, l'intérieur et l'extérieur, la fermeture des pyramides

illustration extraite de l'ouvrage de Grinsell

The Superstructure

(a) Interior (Old Kingdom Pyramids)

(1 ) The Core. In the earliest pyramids, such as the Step Pyramid of Djeser at Saqqâra and the pyramid of Snefru at Maidûm, the substructure was covered by a mastaba-like edifice, either rectangular (Djeser) or square (most other examples), having a slope-angle of 75-80 degrees. The Step Pyramid was formed around this core by the addition of masonry both vertically and horizontally, giving the impression of a series of mastabas one above the other. Until the early part of Dynasty XII the core of the pyramids was usually of blocks of coarse limestone, faced with rather larger blocks.

(2) The Intermediate Walls. The royal tombs of Dynasty II were conjecturally reconstructed by Reisner with a series of walls outside of the mastaba-core. From Dynasty III onwards these walls occur in every pyramid sufficiently ruined to display its structure until the end of the Old Kingdom and probably the beginning of the Middle Kingdom. According to Petrie they were 'for binding the structure, and in a traditional succession from the primitive mastaba’. The intermediate walls were placed one outside the other, the outer ones being lower than the inner, on all four sides of the core, thus producing a stepped-pyramidal form. The slope angle of each wall was about 70 degrees, but steeper slopes occasionally occur.
Each intermediate wall consists normally of two parts :
a. The body of small blocks of coarse limestone.
b. The casing of large blocks of finer limestone.
The Step Pyramid at Saqqâra is essentially a very high mastaba core surrounded by a series of walls. The tops as well as the sides of these walls were cased with fine white limestone blocks which were dressed and smoothed into the finished stepped structure. The intermediate walls of Snefru at Maidûm were likewise cased with fine white limestone which was dressed smooth although later hidden behind the final casing of the pyramid ; for in this instance the gaps between the steps were filled in to form the earliest known true pyramid. From Dynasty IV onwards the facing of the intermediate walls was left rough. The construction of the various walls probably proceeded together at the same time and more or less at the same level. Good examples of exposed intermediate walls are to be seen at the Maidûm pyramid of Snefru, the small pyramids near those of Kheops and Mycerinus at Gîza, and the pyramids of Abu Sîr.

(3) The Backing Stones. After filling in the triangular gaps between the steps of the intermediate walls, it was necessary to add well-laid masonry which was to constitute a backing for the casing of the pyramid. These backing stones are nearly always of fine white limestone. In some instances the fitting together of the backing stones does not fall far short of the quality of jointing of the casing blocks. The outer faces of the backing-stones were often inscribed with graffiti written thereon by the architects, builders’ scribes and others. Some of them are of the nature of vertical and horizontal lines with extended triangles, and measurements in cubits ; these are evidently for measuring the progress of the work and checking the batter of the pyramid. Other graffiti, such as one on the west side of the pyramid of Neit at S. Saqqâra record the state of advancement of the building on a particular date. Others give the names of the crews of workmen employed, the name of the king whose tomb was being built, and other details.


(b) Interior (Middle Kingdom Pyramids)

Instead of having a core, intermediate walls, and backing stones, the pyramids of the Middle Kingdom were nearly all built on a different principle, the body of the pyramid being constructed of a series of walls radiating from the centre, their interstices being filled with mud bricks or other materials.
(1) The Interior Walling consisted of two walls crossing at right angles parallel to the sides of the pyramid, which divided it into four sections. Diagonal walls caused a subdivision into eight sub-sections, and often there were additional walls which made sixteen divisions in all. At the pyramid of Sesostris I at Lisht the walls were of limestone ; at the pyramid of Sesostris II at Lahûn the lower parts of the walls were of limestone and the upper parts of mud-brick ; in most other Middle Kingdom pyramids the walls were entirely of mud-brick.
(2) The Filling of the divisions between the interior walls was of mud-bricks or sand and rubble.
(3) Backing Layers and Backing Stones, between the body of the pyramid and the casing was a series of carefully laid bricks or ‘backing layers’ and backing stones, which were necessary in order to receive the limestone casing blocks.
(4) Making of Mud-Bricks. The manufacture of mud-bricks in ancient Egypt was similar to that of to-day. The method consists of getting a quantity of Nile mud or alluvium, mixing it with water until the resulting mass becomes plastic, and adding sand or chopped straw to give coherence and to prevent the bricks from warping when drying. The wooden mould (of which ancient and modern examples are identical) is rinsed with water to prevent the mud from sticking to the inner sides, and is then filled with the mud mixture. The resulting bricks are left in the sun for four or five days to dry, after which they are ready for use. By this method, which is best carried out by subdivision of labour (one mixing the mud, one man moulding, and one laying the bricks to dry) 4,000-6,000 bricks per day can be produced by three men.
The length of the bricks in the Middle Kingdom was twice their breadth, which enabled them to be laid ‘headers and stretchers.’ (...)

(c) Exterior (Old and Middle Kingdom).
(1) The Casing.
The casing of most pyramids was of fine white limestone, but granite was used for the first sixteen courses of that of Mycerinus, and for the lowest part of the casing of the pyramids of Khephren, Djedefrê, and Neferirkarê. The casing stones were first of all dressed to a smooth surface on their under sides, and then they were placed in position with the aid of levers. Their tops were next dressed, and marked with incised lines to indicate the position of the stones to be super-imposed. The front sides of the casing’ blocks were dressed last of all, and they were dressed from the apex of the pyramid downwards. This is shown at the pyramid of Mycerinus, where several of the red granite casing blocks are undressed and still have the projecting lugs to receive the positioning levers. On account of the premature death of Mycerinus the dressing of the casing of his pyramid was left uncompleted. The probability that limestone casing blocks were likewise dressed after being placed in position is revealed by a study of the pyramids of Djeser and Kheops ; but Petrie considered that they were sometimes dressed before being placed in position.
(...) In the setting of casing blocks a gypsum mortar was often used, but as a lubricant and not as a cement.
Pyramids of the Middle Kingdom sometimes have their casing blocks joined together with dovetail-cramps as at the pyramid of Sesostris in at Dahshûr. It has already been noted that during Dynasty III the masonry of the superstructure of pyramids tended to be inclined downwards from the casing towards the core. From Dynasty IV onwards the masonry was usually laid in horizontal courses on a level plane.

(2) The Pyramidion.
The apex of the pyramid was formed by a single block or pyramidion. In the Old and Middle Kingdoms this pyramidion was probably always of a black or grey-black stone, especially black granite (Ammenemes III) or basalt (Khendjer II). At other times pyramidia were occasionally of white limestone (Intef, Dynasty XI, in British Museum ; and the pyramidia of some of the private tombs of Dynasties XVIII and XIX at Deir el Madîna, Thebes). Pyramidia usually have a boss or disc projecting from their base, so that they could be firmly secured on a corresponding hollow cut in the stones on which they were to be placed.
No pyramidia of the Old Kingdom have yet been found ; but in his biographical text Uni relates how he was sent by King Mernerê to Ibhet (in Upper Egypt) to bring ‘the costly and splendid pyramidion for the pyramid called ‘‘Mernerê shines and is beautiful". The Egyptian Museum at Cairo contains nearly all the known pyramidia of Middle Kingdom ; they include the polished black granite example of Ammenemes III (Dynasty XII), and those of Khendjer II, his unknown neighbour, and Menneferrê (Dynasty XIII). The two examples at the foot of the pyramid of an unknown king adjoining the pyramid of Khendjer II are both unfinished and one of them still possesses the red guide lines intended to assist the mason in his work.


The Closing of the Pyramid

The closing of the tomb against robbers after the king had been buried presented a serious problem to the kings and their architects ; it worried Kheops so much that he was for ever seeking the locks of the Sanctuary of Thoth, 'to make for himself the like thereof for his "Horizon" (i.e. pyramid).'
The chief methods of closing the pyramids after the interment were as follows : 

(a) Sealing the Sarcophagus
The sarcophagi of Unis and Pepy II, and probably others, were intended to receive a wooden coffin let into it by ropes, grooves for which are still visible in those sarcophagi. Previous to the burial, the sarcophagus lid rested on mud-brick walls beside the sarcophagus (Old Kingdom), or was supported above it by piles of stones (Middle Kingdom). The lid was fixed on to the sarcophagus by an ingenious method combining oblique bevelling of three sides with the slotting of the fourth side, the fitting being assisted by the use of a resinous substance which served as a fixative as well as a lubricant. From a glance at Fig. 8 (cf. ci-dessus) the difficulty of breaking into a sarcophagus closed in that manner will be readily understood.

(b) Sliding the Portcullis Slabs
The horizontal passage leading from the sarcophagus chamber nearly always contained between one and three portcullis slabs. In the Old Kingdom they were of granite and dropped down vertically ; in the Middle Kingdom they were often of quartzite and slid across a slightly inclined transverse plane. In each case their object was to block the horizontal passage against intruders.
The methods of lowering the vertical portcullis slabs are as yet not fully understood. Borchardt suggested that they were sometimes suspended and subsequently lowered by a pulley and palm-log device. In other instances they were propped up by stones until the interment had been made, and then gradually lowered by removing the stones, assisted by levering. The latter was certainly the method intended to be used in the unfinished mastabas at Maidûm, the portcullises of which were never lowered, and were still propped up by stones when discovered by Petrie.

(c) Blocking the Ramp
Nearly every pyramid has a ramp extending downward from the entrance to the horizontal passage. After the portcullis slabs in the horizontal passage had been lowered, the ramp was filled with masonry. Nearly all the pyramids have since been reopened and their ramps cleared out, but the following instances of blocked ramps are on record :
(1) Pyramid of Kheops ; Vyse stated that the sloping passages were blocked with solid masonry for their whole length.
(2) Pyramid of Khephren ; Vyse stated that the lower entrance and passage were completely filled up with solid masonry, closely jointed and cemented ; the first stone was ten feet long, and the others six or seven.
(3) Pyramid of Snefru at Dahshûr still has the western entrance and most of the western ramp blocked with masonry.
(4) Pyramid of Ammenemes I at Lisht had the ramp blocked by granite monoliths.
(5) Pyramid of Sesostris I at Lisht had the ramp filled with obelisk-shaped granite monoliths, each between 7 and 9 metres long. As each was slid down the ramp with the pointed end foremost it crashed into its predecessor, causing the pointed ends to become truncated and fissured.
(6) Pyramid of Neuserrê at Abû Sîr still has two blocking-stones in the ramp.

d) Concealing the Entrance.
The entrance to each pyramid was concealed from recognition by being blocked with skilfully fitted masonry. Instances of flap-doors, although authentic (as in the pyramids of Snefru and Kheops, are most likely posterior to the construction of the pyramids. Concealment of the entrances to pyramids was assisted by the natural tendency for blown sand to accumulate to a much greater extent in the centre of each side than at the corners. This tendency is clearly shown on air-photographs of pyramids.

extrait d' Egyptian Pyramids, 1947, par Leslie Grinsell (1907-1995), archéologue et conservateur de musée anglais. Durant la Seconde Guerre mondiale, il a rejoint la Royal Air Force et a servi en Égypte, où il s'est familiarisé avec les vestiges archéologiques de l'Égypte antique.