(63) Mon 24 Nov 97 19:10 By: Mike Pell To: All Re: aws - [1/3] tablets St: ------------------------------------------------------------------------------ @EID:32ed 23789940 @MSGID: 1:244/506 00155b38 Computed Tomography (CT) and Archaeology - Research Project Nachum Applbaum The Study of Cuneiform Text, Written On Clay Tablets Sealed in Clay Envelopes With The Aid Of CT. The study of the cuneiform texts sealed in clay envelopes was always extremely limited. Archaeologists had to destroy the outer envelopes in order to get to the inner tablets. The envelopes, besides being valuable artifacts in their own right, have on their outer face the stamped seals of witnesses to the validity of the contents within. Thousands of clay envelopes remain sealed and unread; begging research, in museums and private collections all over the world. Our primary goal was to find a nondestructive tool that would allow us to read the cuneiform texts without damaging the envelope. We felt that if we succeeded in finding such a nondestructive tool we could open new avenues in archeological research for years to come, not only in the study of the contents of the clay envelops, but in a wide range of other research projects. We now believe that we have found a very good example of that kind of nondestructive tool. CT has allowed us to read the contents of clay envelopes and has proven to be useful in preliminary studies of other areas of archaeological research. Some background material on cuneiform tablets sealed in clay envelopes For those who may not be familiar with this type of artifact, a few words of introduction will be helpful. Understanding the nature of the clay tablets and envelopes will allow you to appreciate the technical problems we faced. Over two millennia before the invention of the Hebrew alphabet the scribes of ancient Iraq developed a writing system, we have named "cuneiform". Cuneiform writing was impressed onto a clay tablet by a scribe with a reed stylus. The envelopes and clay tablets upon which we have been working are economic documents written in the Sumerian language - to be exact, legal receipts from the Ur III period, dated to the 21st century BCE. The kings of this dynasty, whose capital is traditionally identified as the Ur of the Chaldees of Genesis, directed a royal nationwide bureaucracy which is known to us from the literally 10's, if not 100's of thousands of Ur III documents, that are in public and private collections all over the world. It appears that as a general practice, scribes prepared economic documents by impressing their signs with reed styluses directly onto the obverse and reverse faces of wet clay tablets. The witnesses to the transaction then pressed their cylinder seals, which bore not only the identity of its owner but often, also, glyptic designs. These seals also have unique artistic value. The tablet was then dried in the sun leaving an official witnessed record of this economic transaction. During that period of Ur III scribes popularized the use of the clay envelopes in order to insure the integrity of the document. The tablet upon which the transaction was recorded was then wrapped in a pie crust thick piece of clay . This wrapping served as a clay envelope or case. On the exterior of the envelope the scribe would copy the inscription that he had written on the face of the tablet inside the envelope. The witnesses would then affix their seals over the cuneiform inscription attesting to the fact that the transaction recorded on the exterior of the envelope was indeed one and the same as that on the tablet enclosed therein. All possible precautions to insure the integrity of the document inside the envelope were taken. We find that the cylinder seal impressions of the witnesses and contracting parties were affixed on all six sides of the envelope. These seals on the envelope must have been very important. The use of clay in the recording of important economic transactions offered an element of safety that paper could not give. The placing of the clay tablet into a tamperproof envelope (casing) and the affixing of the seals on all its sides, made it tamperproof with almost no chance of forgery. The current state of the art in reading Ur III envelope texts is to copy or photograph the text and seals on the exterior of the envelope and then break open the envelope to "get at" the text inside. The study of the document, therefore, requires the very physical destruction of an important part of that self-same document. This destruction, is irreversible. There is no way of opening a clay envelope without damaging its seals and text in the process. [continued....] | AmiQWK 2.9 - FREEWARE | ... --- PCBoard (R) v15.4/M 5 Beta * Origin: The GameBoard BBS - 905ú689ú3982/9409 - BurlingtonúONúCANADA (1:244/ 506) SEEN-BY: 12/12 218/103 890 1001 270/101 353/250 396/1 3615/50 51 3804/180 @PATH: 244/506 99 12/12 396/1 3615/50 218/1001 ------------------------------------------------------------------------------ (64) Mon 24 Nov 97 19:10 By: Mike Pell To: All Re: aws - [2/3] tablets St: ------------------------------------------------------------------------------ @EID:36e9 23789940 @MSGID: 1:244/506 00155b47 2/3 Previous Radiological work done on Envelopes Ralph Alexander MD. and Robert Johnston from the Rochester Institute of Technology published the result of a research project in which they make use of Xeroradiography on archaeological artifacts. We found that they were able to obtain images with partial success. This team tested a clay tablet sealed in a clay envelope and published a picture of their results. It seems that their results were somewhat better then those achieved with conventional X-rays and tomography. Their technique, however, did not produce a picture clear enough to allow the reading of the text inside the envelope. See: Ralph Alexander MD. and Robert Johnston, & quot;Xeroradiography of Ancient Objects: A New Imaging Modality & quot;, in (J.S. Olin & amp; A.D. Franklin eds.) Archaeological Ceramics, Washingtom 1982, pp. 145 - 154. Testing with Computed Tomography (CT) Where as all previous imaging modalities in Medicine such as Radiography are simple geometric projections of the object onto detectors such as film, this technique uses multiple planar projections. These planar projections are mathematically recombined by a digital computer to provide a cross sectional image of the object. The reason we felt that CT scanning would give us better results than the earlier approaches we experimented was that in CT scanning, X-rays pass through the subject at different angles, eliminating superimposition and enabling individual structures to be viewed in insulation. CT also detects subtle differences in the density of the structures observed and presents these on screen in graduated shades from white, for dense substances such as bone or metal, through a succession of grays to black. We used a high resolution 3rd generation CT scanner - an Elscint 2400 elite scanner, with a bone algorithm for reconstruction of the raw data, a image matrix of 512 x 512 and thin slices of 1.2 mm. The scanner examines the envelope in a series of lateral "slices". The computer then uses the data to create an image of the object. In order to maximized our imaging parameters to get the best possible image, we were willing to sacrifice contrast, radiation dose and signal to noise ratio to get higher resolution and sharp edges. We thought that we could do that because the clay in the tablet is very dense and with the air in the impressions have the highest contrast possible. We also did overlapping images on some of the tablets to get more data for reformatting in curved planes. Assuming that the slices are properly stacked one on top of the other with minimal movement or change in other imaging parameters) it is possible to select voxels in other planes than the one in which they were originally obtained. In this way it is possible to obtain images in orthogonal planes (that is at 90 degrees to the original plane) or nonorthogonal (oblique) or even curved. In general, using curved planes may be a labor intensive endeavor as the contour of the object must be carefully traced on multiple levels to be able to bring out as much information as possible. This is especially true with the surface of some of the tablets which appear to be uneven. We feel that as far as the scanning process is concerned we have reached adequate results. In addition, we are at present also experimenting with the reconstruction of the manufacturing process use by the scribes in the production of the envelopes. We have found that the CT images not only supply us with an image of the text, but they also supply us with very valuable information about their manufacturing technique. We are experimenting with the reconstruction of the process used by the scribes to make the envelopes based on this information. [continued...] | AmiQWK 2.9 - FREEWARE | ... --- PCBoard (R) v15.4/M 5 Beta * Origin: The GameBoard BBS - 905ú689ú3982/9409 - BurlingtonúONúCANADA (1:244/ 506) SEEN-BY: 12/12 218/103 890 1001 270/101 353/250 396/1 3615/50 51 3804/180 @PATH: 244/506 99 12/12 396/1 3615/50 218/1001 ------------------------------------------------------------------------------ (65) Mon 24 Nov 97 19:10 By: Mike Pell To: All Re: aws - [3/3] tablets St: ------------------------------------------------------------------------------ @EID:f514 23789940 @MSGID: 1:244/506 00155b55 3/3 Testing with Conventional Tomography We then went on and tried to make use of conventional tomography. Conventional tomography is a special technique that blurs out the shadows of superimposed structures to show more clearly the principal structures being examined. The sharpness is not improved. It is a controlled blurring that leaves some parts of the i Testing with conventional Xray Conventional Xrays of the envelopes only help to reveal that there is a tablet concealed inside the clay envelope. These X-rays did not and could not reveal the text itself. This is because the limitation of conventional plane X-rays is that all structures through which the rays pass are superimposed on the image produced, making it difficult to distinguish particular features. This project has been supported by the Israeli National Center for Cooperation between the Sciences and Archaeology | AmiQWK 2.9 - FREEWARE | ... --- PCBoard (R) v15.4/M 5 Beta * Origin: The GameBoard BBS - 905ú689ú3982/9409 - BurlingtonúONúCANADA (1:244/ 506) SEEN-BY: 12/12 218/103 890 1001 270/101 353/250 396/1 3615/50 51 3804/180 @PATH: 244/506 99 12/12 396/1 3615/50 218/1001