The Introduction of the Lapidary Engraving Wheel in Mesopotamia

Article excerpt

One of the most significant advances to have been made in early lapidary technology was the introduction of the bow-driven engraving wheel. The high-speed cutting action, allowed by rotary motion, made possible substantial improvements in the efficiency of working hard stones. However, there is uncertainty concerning the date of this key invention and its adoption in the Near East. Early in this century, Ward (1910: 9) and Frankfort (1939: 5) proposed a date in the 2nd millennium BC while, for the past 25 years or so, a much earlier date in the second half of the 4th millennium BC has generally been assumed (for example, see Nissen 1977: 16; Gwinnett & Gorelick 1979: 25-7; Collon 1986: 13-14). These views have generally been based upon the interpretation of the designs cut into stone cylinder seals.

Cylinder seals (FIGURE 1) developed alongside the cuneiform system of writing, beginning sometime around 3500 BC, and they provide a more or less continuous record of lapidary methods over three millennia. Amuletic and decorative functions were also associated with cylinder seals and they were perforated longitudinally, so that they could be suspended and worn by the owner. The principal methods used to drill these perforations have been identified by Gwinnett & Gorelick (1987). Furthermore, the fine detail preserved in the intaglios of the seals is ideal for study of ancient lapidary technology and a systematic investigation by the present authors has shown that it is possible to identify the methods used to engrave the seals (Sax & Meeks 1995; Sax et al. 1998; see also Sax & Meeks 1994). The various techniques, tools and abrasive materials can usually be recognized from the characteristic morphology or `tool marks' of the engraved features.

[Figure 1 ILLUSTRATION OMITTED]

It emerged in our earlier investigation that simple flaking techniques of engraving prevailed in the late 4th millennium BC and throughout the 3rd millennium BC, with no evidence for the use of wheel-cutting techniques. However, wheel-cutting became the dominant technique in the 1st millennium BC. We have therefore focused the present study upon the changes that occurred during the 2nd millennium, with the aim of establishing the chronology of the introduction of the wheel and the other technological changes with which it was associated.

Methodology

Identification of the materials of the 2500 or so seals in the collections of the British Museum has shown that increasing proportions of harder stones, such as rock crystal, chalcedony, carnelian, agate and other varieties of quartz, were worked with time (Sax in Collon 1982; 1986; in press; Sax 1991; Sax & Middleton 1992). Quartz was the hardest material commonly worked (Mohs' hardness, H=7) and it is likely that the difficulty of working it stimulated innovations in technique which were less advantageous to the working of seals in softer materials. The investigation into engraving methods therefore concentrated upon the 400 or so quartz cylinder seals in the British Museum collections. On stylistic grounds, they range from c. 3100 BC to c. 400 BC (Collon 1982; 1986; & work in progress; Matthews 1990).

Following the approach of Sax & Meeks (1995: 26-7), a chronological survey of the intaglios on the seals was made with a low-power binocular microscope. Seals that were considered to represent key stages in the application of engraving techniques were selected for examination using scanning electron microscopy (SEM). To avoid the need to apply a conductive coating to the seals, detailed impressions were made with a silicone moulding material. As the designs on the seals were worked in intaglio, the engraved features appear on moulded impressions as positive features. Hence, SEM images of the impressions (FIGURES 2-3 & 5) show the intaglios `in reverse' with protrusions on the image representing depressions in the original seal. …