"Iron and Lead"

A study of the slots and fastening leads
on the underwater Pharos site
Mourad El Amoury
Last update, March 2004

The Lighthouse of Alexandria has still not revealed all its secrets. This construction has given rise to numerous studies that have not actually looked at the material remains that are never the less so abundant under water at the foot of the fortress of Qaitbay. The Centre d’Etudes Alexandrines, under the direction of Jean-Yves Empereur, has been tackling this since 1994 by way of underwater excavations with the aim of presenting an exhaustive architectural study of the some 3000 sunken blocks. Since 1998, a study of the construction methods, as represented on the one hand by the slots apparent on the architectural elements, and on the other by the fastening leads found during the dig, has begun as part of the architectural study.

EArchitectural element in situ showing
fastening slots full of lead.
photo CEAlex, all rights reserved
This research is based upon an analysis of the cavities present on the blocks as well as an analysis of the fastening leads discovered during the dig, with the aim of elaborating a comparative analysis that will permit the extraction of a maximum of and formation regarding the actual construction techniques.
A fastening slot is a sign of construction. It allows for the joining of two juxtaposed blocks in the case of a horizontal fastening, and two superimposed blocks in a vertical assembly. The assemblage thus realised reinforces the cohesion of a construction generally of hard stone against those forces that might damage it. This reinforcement is not necessarily rigid and the use of lead as a joining element gives a certain elasticity, making the stability of the assembly more certain. Lead is a soft metal that melts at a low temperature. This latter quality means that it can be applied easily and provides elasticity as much to the fastening as to the ensemble of the construction. At the same time, a lead coating acts as protection against the oxidisation of cramps and dowels containing iron. In fact, the corrosion of an iron cramp can lead to a block cracking at the mortise that holds it and thus can damage the entire construction.

Drawing by Mourad El Amouri, CEAlex, all rights reserved

Plomb de scellement horizontal : Horizontal lead fastening
Agraphe : cramp Plomb : lead Fer : iron Bloc de pierre : stone block
crampon en queue d'aronde : dovetail cramp vue de haut : view from above
Plomb de scellement vertical : Vertical lead fastening
Goujon-tenon circulaire : circular dowel pin Mortaise : mortise Vvue en coupe : section view
Up till now on the Pharos site the fastening leads studied have been associated to cramps or dowels of a different material, principally iron and bronze.
dowel, photo © CEAlex, DR cramp, photo © CEAlex, DR

Lead survives better underwater than in the open air and can give us a lot of information about the material, shape and type of break of the cramp that it held. Thus, the analysis of the fastening lead of the Pharos site rests upon three elements:

  • The fastening cavity on the block.
  • The lead, medium of the system, that allows for the reconstitution of the shape of the cavity and the cramp.
  • The cramp, whose shape is stamped in the lead
At this stage of the study, it is still uncertain whether the slots and the fastening leads are examples of purely Greek or Egyptian technique or indeed a mixture of the two. In fact, if it is taken that the construction of Alexandria and its buildings was Hellenistic, we, never the less, know nothing about the craftsmen and workers who laboured under the orders of such patrons as Sostratos of Cnidus. If their experiences cannot be felt through the visible elements or culturally representative decorations of a construction from the beginning of the period of Macedonian colonisation, they could perhaps be expressed within the techniques employed by an Egyptian savoir-faire. Thus the applied techniques might show the influence of Egyptian builders. Given that granite was the material of choice for the Egyptians, it could be that construction techniques developed over the millennia before the Greeks came to influence these latter in their adaptation to this new material.