The most serious flaws in the obelisk are those lettered a, b, c, d, k, m, o and p; any one of these would give one seriously to think as to the advisability of abandoning the work forthwith. {7} Fissure a meets fissure b and settles, once and for all, that the pyramidion must be set back at least half a metre. Fissure c is even more radical. Fissures d, e and f all seem to have connection with one another and make a considerable reduction in width necessary; those between k and m carry a similar warning on the south side, while m and o necessitate shortening the obelisk from the butt end. The last fissure completely separates the corner of the obelisk from the rest.
It might well be asked: Why was the work continued so long after such bad fissures had been discovered? The answer may be that none of these fissures appeared to be serious, even a short distance above the present level of the face of the obelisk. The north and south trenches do not give evidence that the granite was in a bad state, except at ab, l, o and p.
It is likely that the black line π, drawn across the base of the obelisk to shorten it by over 2 metres, was made by the original workers; this is indicated by the fact that, below this line, the hammer-dressing has been left in a rougher state than that on the remainder of the face of the obelisk; further, the trench, which was intended to separate the base of the obelisk, was abandoned earlier than those on the north and south sides, probably as soon as the fissures shewed themselves to be deep.
There is a curious fissure in the hole F on plate [I] which runs downwards and slightly inwards to the obelisk. Like fissures k to m, it would of itself necessitate a reduction in the original width. It appears, at first sight, that this is the beginning of undercutting the obelisk, but it is not at the level at which this would be commenced.
(8) It would not be out of place, perhaps, to speculate for a moment on the method of obtaining a flat surface along the upper face of the obelisk. I think the method used was by means of boning rods—the method used to-day. For the benefit of those not acquainted with their use, a brief description will suffice. Boning rods are a set of equal, usually T-shaped pieces of wood. One is held upright at each end of the surface which it required to straighten. A man standing at either end, if he sight along the top of these boning rods, can see if a third boning rod, placed anywhere between them, is above or below the line joining them. Thus the surface can be tested anywhere along the obelisk until it is made to slope evenly down along its whole length.
Boning rods for dressing moderately large blocks of stone are shewn in PETRIE, Tools and Weapons, plate XLIX, B 44–46. These measure only about 3 inches high and their tops were connected by a cord. In the case of an obelisk, the cord would be useless owing to the sag, so it seems probable that the sighting method described above was that employed by the ancient Egyptians.
In the setting out of the obelisk, no allowance is made for the slight convexity or entasis, in a longitudinal and transverse sense, which is to be observed in most of the known obelisks. If there was to be a convexity, it was made at a later stage [4]. {8}
[4] It will be noticed in plate [I], nos. 2 and 3, that the slight convexity across the obelisk seen in some places, does not extend the whole length, neither is it even as regards either edge.
(9) When the face of the obelisk had been made fairly flat by hammer-dressing, lines were scratched on it with a chisel, and filled in with black paint. The remains of the lines for the original scheme are clearly traceable. These are shewn on plate [I], α and β. How much reduction was allowed for as regards the final dressing and polishing, we do not know; it was probably only the matter of a couple of centimetres. At the west end of the south trench the reduction of the side of the obelisk to the guide line has been begun. This can be seen at J to K on plate [I]. It now forms a kind of bevel and, as far as it extends, obliterates the vertical markings on the wall of the trench. On the east end of the north trench the trench itself has been moved inwards, from G to H, to be nearer the guide-line. The reason may either be that the workers found themselves too far from the guide-line, or that the guide-line was changed during the progress of the work, perhaps through fear of a fissure.
Before the original workers abandoned their work they seem to have made several attempts to set out a slightly reduced obelisk, which would avoid all serious cracks by reducing the length and thickness of the original design. This is seen in the lines γ δ ε ζ and the transverse lines ι κ λ μ. The last four lines are so faint that they can only be seen just after sunrise or before sunset, and it is not clear with which of the longitudinal lines they connect. On the south side the lines are quite clear, but on the north side there seem to have been more lines even than those shewn on plate [I]. These lines γ δ ε ζ, do not lie at equal distances from either of the two centre lines η and θ.