The Aswân Obelisk / With some remarks on the Ancient Engineering

by Reginald Engelbach

Fig. 1.—Typical wedge-slots.

Wedge-marks may be seen on plate [III], no. 3, on the left of the picture [2]. Typical examples are shewn on plate [III], no. 2, and in figure 1. In nearly every case I observed, a small trench had been cut out by chisels along the proposed line of fracture, presumably to get below the surface, which is often decomposed by exposure, and which would crumble instead of tearing the stone apart. As to whether these wedges were of wood, and made to expand by wetting, I am not certain, but I believe that they were not, the reason being that the slots always taper inwards, and it appears to me that a wetted wedge would tend to spring out rather than exert a lateral force on the stone. In the only case where I have seen wetted wedges used (experimentally on limestone), the wedge-slots were cut with parallel walls.

[1] In some cases a ferruginous (?) stratum in the granite has decomposed the rock with an appearance of its having been burnt. Long exposure of the rock also rots it to a considerable depth, but in the majority of cases where the rock has been removed without wedges or chisels, neither of the above causes can have anything to do with it.

[2] An examination of the wedging-off of blocks in the quarries about Aswân shews that often the wedges have acted perfectly, but the block has not been removed. A crowbar acting in each slot would be ample to remove most of these. Can it be that the crowbar or jemmy of metal was not known?

Assuming, then, that hammered metal wedges were used and not wooden wedges made to expand by the action of water, it remains to be seen whether the plug-and-feather method, such as is used to-day, was employed, or whether the metal wedges engaged with the stone without the thin sheets of metal on either side which we now call ‘feathers’. The advantages of the plug-and-feather method are that it reduces the width of the slot at the top, leaving it wider below and hence to a large extent preventing the sharp edge of the wedge from touching the bottom of the wedge-slot, and that, since the faces of the feathers are smooth, it tends to {5} obtain the maximum advantage of the lateral force exerted by the wedge in the most evenly distributed way and with a minimum of friction. Now nearly all the ancient wedge-slots appear perfectly smooth inside—just as if they had been polished. This would be a disadvantage in using feathers, as there would be a greater tendency for them to jump out at the first blow. Nothing seems to be gained by polishing. Personally I favour the assumption that the Egyptians used the plug-and-feather, but the question is best left open for the present for lack of conclusive evidence. Photographs of two iron wedges from the Ramesseum are given in PETRIE, Tools and Weapons, plate XIII, B 16, 17. They appear to date to about 800 B. C. Feathers, of unknown date, but probably late, are given in the same volume on plate XIII, B 22, 23. It is a bare possibility that the smoothness of the sides of the wedge-slots is due to the fact that the slots were made without chisels, such as by scraping the granite with emery-stone, or that after they had been roughed-out by chisels they were finished by this means.

Sometimes, along a crack, enormous wedges were used, the largest I noticed being 0 m. 25 cent. long, spaced one metre apart. In any case the largeness of the wedges leads us to suppose that the Egyptians must have had large hammers. I do not think that the sledge-hammer, such as we use to-day, was known to the Egyptians, though mallets were common. I believe it likely that heavy rammers, used vertically by more than one man, must have been used to make these wedges act. Mr. C. Firth has pointed out to me a black granite hammer found at Saqqârah, now in the Cairo Museum. Though this example is of the Old Kingdom, it seems quite likely that a similar hammer was used for driving in the wedges. A photograph of the hammer is shewn in plate [IV], no. 2. To-day the quarrymen use very small fat steel punches in conjunction with a sledge-hammer. Some large wedge-marks are seen in plate [III], no. 2, at the top of the picture.

(5) It seems that the intention of the Egyptians was to leave the north wall of the north trench at a level slightly above that of the obelisk. The exceptions to this are the wedged-out block seen on plates [I] and [II], no. 2 at A, and the (now) entrance to the bottom of the north trench at B. I believe these blocks to have been removed at a date later than that of the obelisk; the block A has been wedged out by a long channel instead of separate slots, while at B it is obvious that stone has been removed for building, since the inner face has been chisel-dressed. Near here, too, I found a block containing a ‘jumped’ hole blackened by gunpowder. Had the ancients wished to remove the trench wall at B, there is a crack running along it parallel to the ground, which would make its removal an easy matter by burning from the outside [3]. It seems, therefore, that the north wall of the north trench was intentionally left; the probable reasons are discussed in section [23]. It will be noticed, in plate [II], that the top of this wall has been roughly hammer-dressed near the butt, and to a certain extent near the pyramidion. How far it was intended to reduce the south wall of the south trench is not certain; it depends on the method to be used in getting the obelisk out of the quarry, and is dealt with in sections [21]–23. There are indications that it was to be reduced to a considerable extent. {6}

[3] There is not a trace of burning within 6 feet of the obelisk.

(6) At intervals in the trench around the obelisk there are traces of squarish holes, generally going down to about the level at which the bottom of the obelisk was to be. These are seen more clearly in the south trench than in the north, and can in some cases be traced up the side of the obelisk itself. Besides these there are the deep holes seen at C and D on plate [I]. I believe that the holes C and D were made at the very commencement of the work to study the quality of the granite. The holes along the trench seem to have been made with the same purpose, and as a means of setting out the perimeter of the obelisk. There are indications that they were made when the removal of the top layers of rock were still in progress.

(7) From the beginning of the work on this obelisk, cracks and fissures seem to have given a great deal of trouble and anxiety. Though parting fairly evenly under the action of wedges, the natural fissures of granite are most erratic; a small crack at one level or position may, in a couple of metres, become a fissure into which one can insert the blade of a knife, and conversely, a fissure traceable for 5 metres will suddenly disappear. Hence every fissure or crack, as it appeared, had to be rigorously examined, to see its probable effect on the obelisk when completed. The examination seems to have been made in three ways, which I believe to have been of two dates. The original workers method was to hammer out a depression by means of a spherical ball of about 12 lbs. weight, of a very tough greenish-black stone (section [13]), until the fissure either disappeared or became larger. These examination hammerings can be seen in plate [I] at j, k, n, and p, n being also seen in the photos on plate [II] no. 2 and plate [III] no. 1. In the depression, sometimes at one place and sometimes at two, a small fillet was left at the level of the face of the obelisk, and apparently polished; the object seems to have been to compare the state at the surface with that at the bottom of the depression. The second method was to chisel out a narrow channel right along the crack and to polish it. In some cases, as at the end of fissure i on plate [I], the three red lines, drawn to guide the stone-cutter, can be clearly seen at the end of the channel. It seems likely that the channel method was that used by the later workers who examined the obelisk as to the possibility of extracting a smaller one from it, as the channels are only found in the parts within the area of the smaller obelisk (section [10]). I think that the channels were cut over discolourations and superficial flaws, recognised as such and left by the original workmen. The statement made by Barber, in his The Mechanical Triumphs of the Ancient Egyptians, that the grooves are made at some later date with the intention of cutting up the obelisk, is impossible, as two (h and i, plate [I]) run transversely across the obelisk, where all the wedging and cutting in the world would not part the stone. The line of small punch-holes at H, however, was undoubtedly made in modern or mediæval times to extract a block from the side of the obelisk, and it is a marvel that the obelisk has not been used as a quarry throughout the ages. The third method was to cut with a chisel oblong holes, tapering sharply inwards, on the crack to be examined. It is possible that this was the work of the original party, done in haste on the occasion of an inspection. This method is seen at the base of the pyramidion on plate [I].