Photomicrography and Statistical Sampling of Pseudomorphs after

27 Photomicrography and Statistical Downloaded by UNIV OF CINCINNATI on November 12, 2014 | http://pubs.acs.org Publication Date: July 1, 1989 | doi: 10.1021/ba-1988-0220.ch027

Sampling of Pseudomorphs after Textiles L. R. Sibley , Kathryn A. Jakes , J. T. Kuttruff , V. S. Wimberley , D. Malec , and A. Bajamonde 1

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Department of Textiles and Clothing, Ohio State University, Columbus, O H 43210 Department of Home Economics, University of Texas, Austin, TX 78712 National Center for Health Statistics, Hyattsville, MD 20782 Department of Statistics, University of California—Berkeley, Berkeley, CA 94720

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The nature and extent of pseudomorphs after textiles on a Shang bronze spearpoint are explored by using mapping of the evidence by photomicrography and simple random sampling. The two techniques are designed to increase the rigor of the methodology used to study certain forms of the archaeological textile record that require extensive analysis. Complete linkage cluster analysis and classification and regression tree (CART) of technical fabrication attribute data reveal the presence of unbalanced plain weave silk fabric with areas of float.

THE RECONSTRUCTION OF PAST HUMAN BEHAVIOR

from early textile r e mains continues to challenge the analyst. D e s p i t e recent strides made i n u n d e r s t a n d i n g the basic c h e m i s t r y a n d degradation of textile fibers i n the diagenetic context ( I , 2), there is not yet a rigorous methodology capable o f y i e l d i n g v a l i d a n d r e l i a b l e data w i t h w h i c h to infer h u m a n behavior. Because textiles w e r e u s e d w i d e l y i n n e a r l y a l l facets of the c u l t u r a l system, t h e y p r o v i d e i m p o r t a n t e v i d e n c e of past d e c i s i o n - m a k i n g . Yet t h e i r c o m p o s i t i o n has r e s u l t e d i n differing degrees of survival, i n forms often difficult to analyze.

0065-2393/89/0220-0465$06.00/0 © 1989 A m e r i c a n C h e m i c a l S o c i e t y

In Archaeological Chemistry IV; Allen, R.; Advances in Chemistry; American Chemical Society: Washington, DC, 1989.

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ARCHAEOLOGICAL CHEMISTRY

Downloaded by UNIV OF CINCINNATI on November 12, 2014 | http://pubs.acs.org Publication Date: July 1, 1989 | doi: 10.1021/ba-1988-0220.ch027

W i t h o u t better research designs, textile analysts r u n the risk of h a v i n g p o tentially p o w e r f u l data b e i n g m i s a p p l i e d i n the d e v e l o p m e n t of inferences about the past use of textiles. T h e purpose of the research d e s c r i b e d i n this chapter was to a p p l y two techniques of analysis to the investigation of p s e u d o m o r p h s after textiles, one f o r m of the archaeological textile r e c o r d . S p e cifically these techniques are m a p p i n g textile e v i d e n c e b y p h o t o m i c r o g r a p h y a n d statistical s a m p l i n g of that evidence. A r c h a e o l o g i c a l textiles occasionally o c c u r i n forms that m i s l e a d the a n alyst. T h e m i n e r a l i z e d fabric e v i d e n c e k n o w n as p s e u d o m o r p h s after fabric is one such f o r m . F a b r i c r e m a i n s may be r e c o v e r e d i n pieces c r u m p l e d together a n d m a y e x h i b i t p r o n o u n c e d structural variation. I n such instances, one cannot r e l y o n a series of tests from one area of the fabric to identify characteristics of the e n t i r e fabric. T h e fragmented a n d fragile c o n d i t i o n of archaeological fabrics has l e d to bias because scientists have evaluated parts of fabrics that w e r e accessible a n d of interest. W i t h o u t s a m p l i n g designed to avoid bias, inferences r e l a t i n g to the structure of textile r e m a i n s or the h u m a n b e h a v i o r associated w i t h t h e i r p r o d u c t i o n a n d use m a y b e i n question. T o infer the w h o l e f r o m the part w i t h any degree of rigor requires an assumption that the part (a single observation) represents the w h o l e (textile remains). T h a t assumption s h o u l d not b e made unless data gleaned from analysis of the fragment are o b t a i n e d t h r o u g h p r o b a b i l i s t i c s a m p l i n g procedures, because the alternative of u s i n g a large n o n p r o b a b i l i s t i c sample is difficult to a c c o m p l i s h (3). T h e p o t e n t i a l e r r o r i n h a p h a z a r d s a m p l i n g c o u l d negate the results of v e r y precise i n s t r u m e n t a l a n d t e c h n i c a l fabrication analyses. M a p p i n g the textile e v i d e n c e b y p h o t o m i c r o g r a p h y is another t e c h n i q u e u s e d to study the archaeological textile r e c o r d . M a p p i n g is the p r e p a r a t i o n of an enlarged v i s u a l r e c o r d of adjacent areas of fabric f r o m p h o t o m i c r o graphs, a n d i t allows the investigator to p l o t the m o v e m e n t a n d i n t e r a c t i o n of textile c o m p o n e n t s a n d to study the fabric i n d e t a i l . M a p p i n g also p r o v i d e s the means to trace the spatial relationships of a fragment's fiber-yarn-fabric e v i d e n c e w i t h respect to adjacent fragments or to a m e t a l host. T h e t e c h n i q u e s of m a p p i n g b y p h o t o m i c r o g r a p h y a n d statistical s a m p l i n g i m p r o v e the r e l i a b i l i t y of the data obtained. U s e d together, they strengthen the research design d e v e l o p e d to evaluate archaeological textile remains. E x a m i n a t i o n of archaeological textile e v i d e n c e includes analysis of two classes of e v i d e n c e to y i e l d w h a t is r e f e r r e d to as attribute data. T h e s e data are d e r i v e d f r o m (1) t e c h n i c a l fabrication examinations of the fib e r - y a r n - f a b r i c e v i d e n c e a n d (2) the p h y s i c a l a n d c h e m i c a l analyses of the fiber. B o t h classes of information are necessary to characterize fully the fabric e v i d e n c e , a n d b o t h r e q u i r e p h o t o m i c r o g r a p h y as an i n i t i a l step i n the anal y t i c a l p r o c e d u r e . T h e nature of the information sought leads to different avenues of testing. Because b o t h are essential to the c o m p l e t e u n d e r s t a n d i n g of the textile, the sets of results obtained i n the testing c o m p l e m e n t each other.



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T w o p r o b l e m s s h o u l d be c o n s i d e r e d w h e n c o n d u c t i n g a n investigation that incorporates m a p p i n g a n d s a m p l i n g techniques. O n e p r o b l e m is that the irreplaceable a n d fragile nature of the textile e v i d e n c e demands n o n destructive or m i n i m a l l y destructive procedures. R e m o v a l of enough m i crosized samples to p r o v i d e a statistical sample w o u l d destroy m u c h of the textile. A n o t h e r consideration is that the cost of techniques such as as X - r a y diffraction ( X R D ) or F o u r i e r transform infrared spectroscopy ( F T I R ) w o u l d b e p r o h i b i t i v e w h e n a p p l i e d to a large n u m b e r of samples. Because of these constraints, c h e m i c a l a n d p h y s i c a l data s h o u l d b e o b t a i n e d from a l i m i t e d n u m b e r of locations. T h e s e areas can best b e i d e n t i f i e d once a survey of the e v i d e n c e has b e e n c o n d u c t e d a n d t e c h n i c a l fabrication analyses of e v i d e n c e o b t a i n e d f r o m a r a n d o m sample of locations have b e e n p e r f o r m e d . W e u s e d m a p p i n g b y p h o t o m i c r o g r a p h y a n d statistical s a m p l i n g to e v a l uate p s e u d o m o r p h s after fabric from one S h a n g b r o n z e w e a p o n , a spearpoint ( S p l ) , d a t e d about 1300 B . C . ( F i g u r e 1). T h e spearpoint has b e e n the focus of earlier investigations ( J , 2,4, 5), w h i c h constitute a survey of the e v i d e n c e . T h i s investigation emphasizes t e c h n i c a l fabrication data t h r o u g h s a m p l i n g a n d m a p p i n g , a n d the i m p l i c a t i o n s for future c h e m i c a l a n d p h y s i c a l analyses.

Methodology T h e objective of the study is to d e t e r m i n e the nature a n d extent of p s e u d o m o r p h s o n S p l b y m a p p i n g , w i t h p h o t o m i c r o g r a p h y a n d statistical s a m p l i n g t e c h n i q u e s . T h e " p o p u l a t i o n " to be s t u d i e d c o n s i s t e d of a l l p s e u d o m o r p h s after fabric located o n the spearpoint. A survey p r e v i o u s l y c o n d u c t e d w i t h microscopy i d e n t i f i e d the general location of the m i n e r a l i z e d fabrics. A research hypothesis, d e r i v e d from the survey of e v i d e n c e , gove r n e d the study a n d is as follows: P s e u d o m o r p h s after fabric located o n S p l are fragments of a n u n b a l a n c e d plain-weave type of fabric.

Figure 1. Shang bronze spearpoint (Spl) from the Museum of Anthropology, University of Missouri— Columbia. Reduction: 45 x .


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Data Collection Mapping. N o attempt was made to m a p the e n t i r e area of p s e u d o m o r p h s after fabric; rather, photomicrographs of adjacent location points w e r e r e v i e w e d , a n d two groups w e r e selected for further study. C r i t e r i a for i n c l u s i o n i n the m a p w e r e the p r o x i m i t y to other location points a n d 10.2 X


magnification for the p h o t o m i c r o g r a p h . Slides w e r e d e v e l o p e d as 5- X 7i n . photographs. T h e photographs w e r e p l a c e d u p o n a n e u t r a l - c o l o r e d mat b o a r d a n d fitted together so that yarns c o u l d be tracked across several location points. Sampling. A sample was d r a w n at r a n d o m f r o m a list of r a n d o m l y c o m b i n e d χ a n d y coordinates that i n d i c a t e d location points for p s e u d o m o r p h i c e v i d e n c e . T h e location point is d e f i n e d as the field of v i s i o n at 10 X magnification that a l l o w e d attribute data o c c u r r i n g i n the field to be o b served. T h e spearpoint was p l a c e d u p o n a special microscope stage that h a d a c e n t i m e t e r g r i d system. T h e χ axis was i d e n t i f i e d b y letters A - Y , a n d the y axis was i d e n t i f i e d b y n u m b e r s 1-10. T h e s e combinations of coordinates l e d to the spatial location points or subunits of the site. P h o t o m i c r o g raphy was u s e d to r e c o r d the m i n e r a l i z e d fabric attributes at 101 location points. Before s a m p l i n g , a list of attribute dimensions based u p o n available t e c h n i c a l fabrication i n f o r m a t i o n was c o m p i l e d . T h e d i m e n s i o n of an attribute differs from the attribute a n d is defined as a trait or characteristic capable of s u b d i v i s i o n i n t o n u m e r o u s subcategories (attributes). F o r example, color is a d i m e n s i o n of an attribute; r e d is an attribute. F o r the e v i d e n c e b e i n g s t u d i e d , fiber e n t i t y o r the n u m b e r of fiber entities o c c u r r i n g together nat u r a l l y is an attribute d i m e n s i o n . A t t r i b u t e s of the d i m e n s i o n " f i b e r e n t i t y " i n c l u d e singles, pairs, a n d b u n d l e s . T h e entities form the basis for c o n v e r t i n g fibers i n t o y a r n . T h e attribute d i m e n s i o n s i d e n t i f i e d i n c l u d e d fiber e n t i t y , fiber c r i m p , fiber surface, y a r n t y p e , n u m b e r of y a r n components, y a r n twist d i r e c t i o n , n u m b e r of y a r n systems, y a r n system d i r e c t i o n , type of i n t e r w o r k i n g , layers i d e n t i f i e d , a n d fabric deformation. A t t r i b u t e data w e r e i d e n t i f i e d from the photomicrographs of each l o cation p o i n t i n the sample, a n d each p o t e n t i a l categorical variable (attribute) was r e c o r d e d as present or absent. Because it was desirable to d e t e r m i n e w h e t h e r the e v i d e n c e at the location points was r e l a t e d , the data w e r e subjected to h i e r a r c h i c a l c l u s t e r i n g . T h e measure of dissimilarity u s e d i n the project was the n u m b e r of matches a m o n g attribute measurements that two location points shared. F o r example, two points h a d a d i s s i m i l a r i t y of 0 i f t h e y m a t c h e d o n a l l attribute measurements, and at the other e x t r e m e , the two location points h a d a dissimilarity of 13 (the total n u m b e r of m e a s u r e d attributes) i f they d i d not m a t c h o n any of the measurements. E a c h m a t c h was w e i g h e d as e q u a l l y i m p o r t a n t . I n a d d i t i o n to this i n t u i t i v e measure of


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dissimilarity, w e u s e d c o m p l e t e linkage (also called nearest neighbor), a p r o c e d u r e that tends to form clusters i n w h i c h a l l points w i t h i n a cluster are relatively homogeneous w i t h r e g a r d to t h e i r attributes.


O n c e clusters w e r e d e t e r m i n e d , the next step was to identify w h i c h measures w e r e i m p o r t a n t i n d e f i n i n g the clusters. A classification p r o c e d u r e similar to d i s c r i m i n a n t analysis was u s e d to d e t e r m i n e w h i c h attributes actually p l a c e d a p o i n t i n a p a r t i c u l a r cluster. Because a l l measurements are categorical (presence or absence), a n o n p a r a m e t r i c p r o c e d u r e c a l l e d classification a n d regression tree ( C A R T ) was used. O f the 13 available attributes, three have d i r e c t relevance to the research hypothesis c o n c e r n i n g i n c i d e n c e of u n b a l a n c e d plain-weave fabric. T h e s e attributes are the presence of float i n one set of yarns of a fabric structure, the presence of a p l a i n weave (defined as a repeated s i m p l e alternating) i n t e r w o r k i n g p a t t e r n (1/1), a n d the presence of layers of fabric. I f a l l three are present, there are at least t h r e e possible interpretations: 1. T w o layers of a single p a t t e r n e d fabric are present. 2. L a y e r s of different fabrics are present. 3. L a y e r s of p l a i n fabric a n d p a t t e r n e d fabric are s u p e r i m p o s e d o n one another. A structural p a t t e r n e d fabric is suggested b y the presence of float a n d p l a i n weave together w i t h o u t any layers. I f layers of fabric are o b s e r v e d i n c o n j u n c t i o n w i t h float b u t w i t h o u t 1/1 i n t e r w o r k i n g , t h e n two layers of float fabric are i n d i c a t e d . T h e presence of float b y itself w o u l d suggest a single layer of float fabric, a n d the presence of 1/1 b y itself w o u l d support a p l a i n weave. L a y e r s of fabric w o u l d o n l y o c c u r w h e r e some i n t e r w o r k i n g of fabric e v i d e n c e is present e i t h e r , i n the f o r m of repeated s i m p l e alternating systems or the repeated float progression of alternation. These combinations are s u m m a r i z e d i n T a b l e I. T h e r e m a i n i n g 11 attributes w o u l d define fiber a n d y a r n characteristics, b u t t a k e n b y themselves, do not indicate fabric structure.

Table I. The Six Attribute Combinations for Pseudomorphs After Fabric on Shang Spearpoint Combination 1 2 3 4 5 6

Float

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Layers

Present Present Present Absent Present Absent

Present Present Absent Present Absent Present

Present Absent Present Present Absent Absent


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Results M a p p i n g of the two areas chosen for magnification shows the i n t e r p l a y of two different systems of yarns i n a regular plain-weave i n t e r l a c i n g p a t t e r n . O n e system consistently has yarns that are 1.5 times larger than those of the other system. T h e difference i n the y a r n systems confirms the u n b a l a n c e d p l a i n - w e a v e s t r u c t u r e , w h i c h is observable w i t h o u t magnification as r i b b e d fabric ( F i g u r e 2). O n e of the areas shows the presence of layers of m i n e r a l i z e d remains o n the blade. A section of r e d , i d e n t i f i e d as c u p r i t e i n the p l a i n weave formation, rests o n top of a green or malachite section (6). B o t h formations share the same type of structure, a n d the two layers do not have the same o r i e n t a t i o n w i t h respect to the spearpoint, despite the s i m i l a r i t y i n weave. T h e p s e u d o m o r p h s after fabric w e r e located i n an area r o u g h l y b e t w e e n H a n d U o n the χ axis, a n d b e t w e e n 3.6 a n d 9.0 o n the y axis. T h i s area corresponds to a p p r o x i m a t e l y 5 2 % of the spearpoint's l e n g t h a n d 8 1 % of its w i d t h . E x a m i n a t i o n of the spearpoint d u r i n g the survey phase h a d already i n d i c a t e d shifts i n the geometry of the fabric w i t h respect to the weapon's f o r m (6). O f 101 s a m p l i n g units d r a w n , 11 r e v e a l e d no p s e u d o m o r p h s after fabrics present, a n d two points h a d p s e u d o m o r p h i c evidence that c o u l d not b e i d e n t i f i e d because of b l u r r i n g of the p h o t o m i c r o g r a p h . O n l y the r e m a i n i n g 88 location points y i e l d e d textile information.

Figure 2. Mapping by photomicrography of pseudomorphs after fabric Shang spearpoint (Spl). Magnification: 51 X .


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Inspection of the fabric attribute dimensions for a l l location points r e v e a l e d that certain attributes w e r e e i t h e r absent or unrecognizable. T h e s e attributes are fiber b u n d l e , fiber single, fiber c r i m p , fiber surface, fiber p a t t e r n , y a r n t y p e , a n d y a r n twist d i r e c t i o n . Therefore, these attributes w e r e d e l e t e d from the statistical analysis. T h e r e m a i n i n g attributes w e r e e i t h e r present at a l l location points or e x h i b i t e d variation. These attributes i n c l u d e d the three (layers, 1/1, a n d float) whose interactive effects h a d d i r e c t relevance to the research hypothesis, a n d the f o l l o w i n g fiber a n d y a r n attributes: p a i r e d fibers, 0 twist, c o m b i n e d yarns, y a r n system A , y a r n systems A + B , y a r n systems A + Β + C 4- D , fabric d i s t o r t i o n , r e d , green, a n d black.

Statistical Analysis I n the first c o m p l e t e linkage analysis, the interaction t e r m (layers, 1/1, float) was assigned the same w e i g h t as any of the other relevant attributes. T h e a l g o r i t h m y i e l d e d three clusters ( F i g u r e 3) w h e n there was o n l y one match (or e q u i v a l e n t l y , w h e n the m a x i m u m distance b e t w e e n clusters was 12 " n o matches"). T w o of these clusters accounted for o n l y 13 of the 101 location points. Interestingly, 11 of these 13 points w e r e precisely those a n d o n l y those points that r e v e a l e d no p s e u d o m o r p h s . T h e other two points w e r e those for w h i c h p s e u d o m o r p h i c e v i d e n c e c o u l d not be i d e n t i f i e d . A s such, these two s m a l l clusters w e r e taken together to form the cluster of " i n d e t e r m i n a t e s " . W h e n matches w e r e increased to t h r e e , the b i g cluster of 88 location points was s u b d i v i d e d into three smaller clusters. A cluster c o u l d represent e i t h e r a fabric type or a fabric pattern. W h e n there are o n l y two clusters, a C A R T demonstrates that y a r n system d i r e c t i o n A is the most i m p o r t a n t classification attribute. T h i s infor m a t i o n was not s u r p r i s i n g because y a r n system A i n d i c a t e d the presence of some k i n d of p s e u d o m o r p h after fabric evidence. W h e n the one b i g cluster is s u b d i v i d e d into three smaller ones, attributes i m p o r t a n t i n f o r m i n g the clusters are as follows: T h e presence of layers, w h e t h e r i n c o m b i n a t i o n w i t h 1/1 i n t e r w o r k i n g , w i t h float i n t e r w o r k i n g , or w i t h b o t h , c o m p l e t e l y d e t e r mines one cluster. A n o t h e r cluster is d o m i n a t e d b y no-layer locations h a v i n g at least float present. T h e t h i r d attribute comprises locations w h e r e o n l y 1/1 i n t e r w o r k i n g is present a m o n g the three i n t e r a c t i n g attributes (Table II). T h e two latter clusters are not c o m p l e t e l y distinct f r o m each other, a n d c o u l d reasonably be taken together. T h e nondetection of layers a n d the presence of at least one layer of 1/1 i n t e r w o r k i n g a n d float w o u l d characterize this cluster. T h e classification tree, w h e n the n u m b e r of clusters is four, shows that the m o r e i m p o r t a n t classification attributes, i n decreasing o r d e r of significance, are y a r n system d i r e c t i o n A , float, r e d y a r n , layers, a n d fabric distortion. F l o a t is the o n l y attribute that is found i n a single cluster. T h e r e m a i n i n g attributes w e r e d i s p e r s e d a m o n g the three clusters.



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Table II. Unweighted Attribute Interaction for F o u r Clusters Attributes

Cluster 1

Cluster 2

Cluster 3


Float, 1/1, layers Float, 1/1 Float, layers Float 1/1, layers 1/1 A l l absent

Cluster 4

13.00

T h e second cluster analysis i n v o l v e d attaching twice as m u c h i m p o r t a n c e to the interaction t e r m than to any of the other 12 attributes. W e o b t a i n e d basically the same cluster tree as w i t h the first m e t h o d , w i t h o n l y a few modifications; some cluster breakups w e r e m o r e severe t h a n before, i n d i cating m o r e cluster-to-cluster distinctiveness, a n d some w e r e less severe. Inspection of the tree i n d i c a t e d that there w e r e e i t h e r two clusters, i n w h i c h case one cluster was approximately twice as b i g as the other cluster, or there w e r e three clusters, w i t h the larger cluster s u b d i v i d e d into two clusters. (See F i g u r e 4.) F u r t h e r examination of spatial plots r e v e a l e d no clear separation of cluster, w h e t h e r the n u m b e r of clusters was designated two or three (Figures 5a a n d b). W h e n the n u m b e r of clusters was two, the classification tree s h o w e d that the i n t e r a c t i o n t e r m perfectly d e t e r m i n e d to w h i c h cluster a location p o i n t s h o u l d b e l o n g . W h e n layers w e r e d e t e c t e d a n d e i t h e r 1/1 i n t e r w o r k i n g or float is present, the location p o i n t goes to C l u s t e r 2. W h e n layers is not present, the location goes to C l u s t e r 1. W i t h o u r data set, the cases for w h i c h b o t h 1/1 i n t e r w o r k i n g a n d float w e r e absent w e r e also those cases for w h i c h layers w e r e e i t h e r absent or c o u l d not be i d e n t i f i e d . Statistically, the interaction t e r m a n d the variable c o r r e s p o n d i n g to the detection of layers measure essentially the same effects. Table I I I shows h o w layers c o m p l e t e l y d e t e r m i n e cluster m e m b e r s h i p . W h e n the larger cluster was b r o k e n into two (i.e., a total of three clusters), one subcluster c o r r e s p o n d e d to the i n d e t e r m i n a t e s , a n d the other h a d no layers w i t h e i t h e r 1/1 i n t e r w o r k i n g or float present (see T a b l e I V ) . M o r e o v e r , the c o r r e s p o n d i n g classification l i s t e d the interaction t e r m , or e q u i v a l e n t l y the layer variable, a n d y a r n system d i r e c t i o n A as the m o r e i m p o r t a n t classification variables. W h e n w e c o n s i d e r e d four clusters u n d e r the first setup, it was suggested that two of these four clusters c o u l d reasonably be seen to constitute o n l y one cluster. I n d e e d , the analysis v e r i f i e d this suggestion. E x h i b i t i n g e i t h e r 1/1 or float as the type of i n t e r w o r k i n g i n o n l y one layer is a strong e n o u g h measure of h o m o g e n e i t y to w e l d the c o r r e s p o n d i n g location points. I n e i t h e r setup, there is adequate e v i d e n c e that g r o u p i n g the location points i n t o three clusters is a useful s u m m a r y of the data. T w o of these clusters can be d e t e r m i n e d b y the presence or absence of layers. T h e t h i r d



474


ο

s I Si

1 CO

i

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Pseudomorphs

475

after Textiles

Figure 5. Spatial plots of weighted interaction.

Table III. Weighted Attribute Interaction for Two Clusters Attributes Float, 1/1, layers Float, 1 / 1 Float, layers Float 1 / 1 , layers

Cluster 1

Cluster 2

7.00 9.00

2.00

-

1/1

40.00

A l l absent

13.00

2.00 28.00

-


476


Table IV. Weighted Attribute Interaction for Three Clusters Attributes


Float, 1/1, layers Float, 1/1 Float, layers Float 1/1, layers 1/1 A l l absent

Cluster 1 7.00 9.00 40.00 -

Cluster 2

Cluster 3

2.00 2.00 28.00 -

13.00

layer consists of the i n d e t e r m i n a t e s . Because the indeterminates are of no practical i m p o r t a n c e , there are essentially o n l y two clusters. O f the 88 s a m p l i n g units w i t h p s e u d o m o r p h s s t u d i e d , 77 (88%) c o n t a i n e d e v i d e n c e of 1/1 i n t e r w o r k i n g of the two y a r n systems. F l o a t i n t e r w o r k i n g w i t h o u t any other t y p e of i n t e r w o r k i n g was o b s e r v e d at n i n e locations (10%), a n d seven locations (8%) d i s p l a y e d e v i d e n c e of 1/1 a n d float together. T w o locations contained layers i n conjunction w i t h float i n t e r w o r k i n g , a n d two locations c o n t a i n e d layers, float, a n d 1/1 i n t e r w o r k i n g . T h e attribute "layers of f a b r i c " was f o u n d at 32 location points (36%). T h e i n c i d e n c e of float a n d float w i t h 1/1 i n t e r w o r k i n g o c c u r r e d i n the L - Q area of the χ axis a n d b e t w e e n 4.9 a n d 7.7 o n the y axis. T w o adjacent points [(N.2, 6.2) a n d ( N . 2 , 6.3)] differ i n the " i n t e r w o r k i n g " attribute d i m e n s i o n . T h e p o i n t ( N . 2 , 6.2) is classified as float o n l y a n d ( N . 2 , 6.3) is classified as float p l u s 1/1 i n t e r w o r k i n g . A l l of the micrographs d i s p l a y i n g float w e r e i n the area w h e r e at least the m a i n layer h a d a s i m i l a r orientation across the blade. T h i s area also h a d raised p s e u d o m o r p h s after fabric that suggested a c r u m p l e d fabric.

Interpretation O f the 32 location points w h e r e layers w e r e i d e n t i f i e d , o n l y two points also h a d b o t h 1/1 i n t e r w o r k i n g a n d float; h o w e v e r , this finding d i d not necessarily indicate that one l a y e r contained 1/1 o n l y a n d the other layer contained float only. T h u s , for o n l y two points w i t h i n this cluster (Table IV, cluster 2) can w e possibly suspect that there w e r e two different types of fabrics. F o r the other points i n this same cluster, w e c o n c l u d e d that 1/1 was s u p e r i m p o s e d o n 1/1, or float was s u p e r i m p o s e d o n float, w h i c h is strongly indicative of the presence of o n l y one fabric. F o r the other cluster for w h i c h no layers w e r e i d e n t i f i e d , there was o n l y one type of fabric w i t h some s t r u c t u r a l variation. A cluster is strong e v i d e n c e that there is o n l y one fabric type. O n e question remains: A r e there two types of fabric present, or do the differences


27.

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b e t w e e n clusters o n l y signify a certain type of p a t t e r n i n g w i t h i n a single fabric? T h e latter hypothesis w i l l b e s u p p o r t e d i f the two clusters t e n d not to b e separated spatially. E x a m i n a t i o n of the spatial p l o t suggests there was no spatial separation ( F i g u r e 5 a, b).


S t r o n g e v i d e n c e suggests that o n l y one t y p e of fabric was present; it was an u n b a l a n c e d p l a i n weave. T h e e v i d e n c e also indicates there w e r e areas of float i n t e r w o r k i n g that w o u l d support the p o s s i b i l i t y of structural patt e r n i n g . T h e m i n e r a l i z e d fabric i d e n t i f i e d as an u n b a l a n c e d p l a i n w e a v e located o n the spearpoint s h o u l d b e c o n s i d e r e d a variant w i t h areas of float.

Discussion T h e s a m p l i n g t e c h n i q u e a p p l i e d i n the research project u n e x p e c t e d l y exp o s e d areas of float i n t e r w o r k i n g . T h e s p i n n i n g of m o r e than one y a r n i n a consistent m a n n e r i n c o n j u n c t i o n w i t h 1/1 i n t e r l a c i n g is i n d i c a t i v e of a struct u r a l l y p a t t e r n e d fabric. S u c h p a t t e r n i n g is achieved b y c h a n g i n g the system of i n t e r l a c i n g at c e r t a i n points to p r o v i d e visual variation. H o w e v e r , c o n sistency a n d p a t t e r n i n float i n t e r w o r k i n g became keys to the identification of a fabric as structurally p a t t e r n e d , because flaws or discrepancies i n the i n t e r l a c i n g o r d e r can lead to float. I n the case of the p s e u d o m o r p h i c e v i d e n c e , there is not e n o u g h consistency to confirm a structurally p a t t e r n e d fabric. T h e e v i d e n c e c o l l e c t e d supports the p o s s i b i l i t y of a structurally p a t t e r n e d i n t e r p r e t a t i o n , h o w e v e r . Because the p s e u d o m o r p h s after fabric are difficult to evaluate, caution s h o u l d be u s e d i n identification of fabric structure. Statistical s a m p l i n g c o m b i n e d w i t h cluster analysis is a useful i n v e s t i gative tool because it r e v e a l e d an i m p o r t a n t characteristic, that is, the p r e s ence of float i n t e r w o r k i n g . N o t o n l y d i d the t e c h n i q u e reduce the p o s s i b i l i t y of bias i n selecting points to measure, b u t it also a l l o w e d identification of a structural feature h i t h e r t o u n o b s e r v e d . D e s p i t e the differential s u r v i v a l of m a t e r i a l c u l t u r e i n the archaeological r e c o r d , the r e c o r d is m o r e extensive than p r e v i o u s l y r e a l i z e d , albeit i n c o m p l e t e . T h e archaeologist faced w i t h constraints of t i m e a n d cost m u s t choose w h a t to study. S a m p l i n g based u p o n p r o b a b i l i t y is a tool that is u s e d i n creasingly to reconstruct the past. T h i s tool m a y be a p p l i e d to a n u m b e r of situations or populations. T h e p o p u l a t i o n to b e s a m p l e d m a y be a geographic r e g i o n or a c u l t u r e area (7, 8), it may consist of subunits of a specific site (9-11), it m a y c o m p r i s e attribute traits or variables of artifacts (12, 13), or it m a y b e c o m p o s e d of a specific class of artifacts from a g i v e n site (11, 14). T h e classes of data recoverable f r o m the archaeological r e c o r d (populations) s e e m infinite b u t t e n d to g r o u p themselves into c u l t u r a l , e n v i r o n m e n t a l , and spatial types of i n f o r m a t i o n (J 5). If the attribute analysis h a d r e v e a l e d that the p s e u d o m o r p h s after fabric located u p o n the spearpoint i n d i c a t e d o n l y an u n b a l a n c e d p l a i n weave, t h e n



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the p r o b a b i l i t y of the presence of different types of fabric w o u l d have b e e n low. If, h o w e v e r , e n o u g h variation i n fabric attributes h a d existed, t h e n the possibility of m u l t i p l e fabric types w o u l d have b e e n strengthened. V a r i a t i o n , of course, m a y have b e e n the result of other possibilities such as s t r u c t u r a l p a t t e r n i n g i n one fabric, layers of fabric, or e v e n deformation of fabric structure. G i v e n extensive a n d p r o n o u n c e d variation i n fabric attributes a n d breaks i n the r e g u l a r i t y of p s e u d o m o r p h p a t t e r n i n g , the presence of m o r e than one type of fabric w o u l d have to b e considered. T h e presence of m u l tiples of one type of fabric w i t h r e g u l a r i t y i n attributes cannot b e d i s c o u n t e d , p a r t i c u l a r l y i f there are breaks or discontinuities i n the p s e u d o m o r p h i c e v i dence. C a r e f u l analysis of the e v i d e n c e is essential. T h e research hypothesis is partially s u p p o r t e d because the float o c c u r r e d i n one fabric type as d e m o n s t r a t e d b y cluster analysis: T h e n e w d e f i n i t i o n of the fabric expands o u r k n o w l e d g e of S h a n g fabric p r o d u c t i o n substantially. T h e u n b a l a n c e d p l a i n weave structure p r o d u c e d a ribbed effect o n the surface of the fabric, w i t h the size of the rib r e l a t e d to the size a n d n u m b e r of the yarns (16). I f the n u m b e r of yarns i n one d i r e c t i o n is great e n o u g h to c o v e r the yarns from the other system, t h e n the fabric is c a l l e d e i t h e r warp-faced or weft-faced. W i t h o u t a selvage, w e cannot identify w h i c h of these two possibilities was present o n the spearpoint. H o w e v e r , one w i d e l y u s e d structure f o u n d i n the H a n D y n a s t y fabrics (206 B . C . - A . D . 220) is the w a r p faced c o m p o u n d silk fabric, w h i c h a c h i e v e d its structural p a t t e r n b y float (17). I f the S h a n g p s e u d o m o r p h s after fabric located u p o n the spearpoint are part of a warp-faced, u n b a l a n c e d p l a i n - w e a v e fabric w i t h p a t t e r n i n g , t h e n the S h a n g p e o p l e a p p a r e n t l y u s e d the same w e a v i n g techniques as the H a n , b u t some 1000 years earlier. O n the other h a n d , i f the m i n e r a l i z e d fabric was part of an u n b a l a n c e d plain-weave fabric that c o n t a i n e d w e a v i n g flaws, t h e n the earlier S h a n g w e r e d e v e l o p i n g the w e a v i n g t r a d i t i o n that later e v o l v e d i n t o the H a n warp-faced silk i d e n t i f i e d b y B u r n h a m (17). T h e presence of layers of m i n e r a l i z e d fabric suggests that the silk fabric may have b e e n w r a p p e d a r o u n d the b l a d e , b u t the fabric was a l t e r e d i n the diagenetic context. A l l evidence of fabric was destroyed o n the reverse side of the spearpoint. F u r t h e r m o r e , the shift i n the geometric r e l a t i o n of the layers w i t h the same attributes, as i n d i c a t e d i n the m a p p e d area, tends to support the w r a p p i n g of one fabric rather than the possibility of d o u b l e c l o t h or some other c o m p o u n d fabric variant. T h e H a n warp-faced c o m p o u n d tabby (unbalanced p l a i n weave) has two sets of w a r p that are integrated i n t o one layer a n d may be c o n s i d e r e d a c o m p o u n d fabric w i t h c o m p l e m e n t a r y w a r p (16, 17). T h e reason for the p l a c e m e n t of fabric a n d w e a p o n i n the b u r i a l context remains a c r u c i a l question for reconstruction of past decision making. M a p p i n g b y p h o t o m i c r o g r a p h y a n d s a m p l i n g have assisted i n the t e c h n i c a l fabrication analysis of p s e u d o m o r p h s after fabric f r o m the S h a n g spearp o i n t . T h e two techniques have strengthened the investigative efforts a n d s h o u l d b e useful i n a n a l y z i n g other m i s l e a d i n g forms of archaeological textile


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e v i d e n c e . C e r t a i n r e c o m m e n d a t i o n s for the application of m a p p i n g s h o u l d be c o n s i d e r e d . 1. A v e r t i c a l d i m e n s i o n m u s t be c o n s i d e r e d at each location point. T h e investigator s h o u l d r e c o r d a n d evaluate e v i d e n c e


at a l l levels that are v i s i b l e , rather t h a n o b s e r v i n g o n l y the u p p e r l e v e l of e v i d e n c e i n the field of v i s i o n . 2. A t t r i b u t e d i m e n s i o n s n e e d to b e m o r e clearly d e f i n e d a n d l i n k e d m o r e closely to the i n i t i a l survey i n o r d e r to focus u p o n variation. 3. S e l e c t i o n of sites for the m a p p i n g b y p h o t o m i c r o g r a p h y s h o u l d occur after the s a m p l i n g a n d cluster analysis are a c c o m p l i s h e d . Results of s a m p l i n g c o u l d suggest certain areas to b e s t u d i e d i n greater d e t a i l . 4. T h e use of a stratified r a n d o m s a m p l i n g t e c h n i q u e w o u l d b e useful. T h e next stage i n the research project w i l l focus u p o n those location points w h e r e significant variation exists, or w h e r e the data c o l l e c t e d are p u z z l i n g . S e l e c t i o n of a l i m i t e d n u m b e r of points for the p h y s i c a l a n d c h e m i c a l testing w o u l d preserve at least part of the evidence and assist i n the search for information about the character of the fiber. A n array of i n s t r u m e n t a l analyses w o u l d b e d e s i g n e d to y i e l d essential data about the textile e v i d e n c e a n d its m i n e r a l i z a t i o n processes.

Summary T h e objective of this study was the d e t e r m i n a t i o n of the nature a n d extent of p s e u d o m o r p h s after fabric located o n one Shang D y n a s t y b r o n z e spearp o i n t . R e i d , Schiffer, a n d Neff (9) n o t e d that the v e r y nature of archaeological research involves s a m p l i n g , b u t the r e a l c o n c e r n is w i t h " h o w to secure a sample that best provides data to answer questions about past b e h a v i o r a l s y s t e m s . " I f the u l t i m a t e goal of studies of p s e u d o m o r p h s after textiles is to infer the use of textiles i n a c u l t u r a l system w h e r e other forms of textile evidence do not s u r v i v e , t h e n the investigator m u s t d e t e r m i n e first the nature a n d extent of the m i n e r a l i z e d e v i d e n c e o n a m e t a l h o s t / o b j e c t . T h e techniques u s e d i n this chapter give us the o p p o r t u n i t y to expand o u r k n o w l edge of one f o r m of the archaeological textile r e c o r d . T h e presence of layers of an u n b a l a n c e d plain-weave silk fabric w i t h areas of float was c o n f i r m e d . A profile of the f a b r i c - m e t a l object relation is a b e g i n n i n g , b u t m a n y m o r e objects a n d p s e u d o m o r p h s w o u l d n e e d to b e e x a m i n e d before generalizations can b e made about c u l t u r a l context. A careful a n d systematic study of one object a n d its p s e u d o m o r p h s w i l l p r o v i d e the basis for m o r e extensive w o r k i n the future.


480


Acknowledgments


T h e w o r k was c o n d u c t e d at the O h i o State U n i v e r s i t y . Initial support for the project was r e c e i v e d from W e n n e r G r e n F o u n d a t i o n for A n t h r o p o l o g i c a l Research. W e express o u r gratitude to the M u s e u m of A n t h r o p o l o g y o f U n i v e r s i t y of M i s s o u r i for loan of the Shang spearpoint. A d d i t i o n a l support of project was r e c e i v e d from T h e Statistical C o n s u l t i n g Laboratory a n d the D e p a r t m e n t of Textiles a n d C l o t h i n g of the O h i o State U n i v e r s i t y , a n d the C e n t e r for Archaeological Sciences of the U n i v e r s i t y of G e o r g i a .

References 1. Jakes, Κ. Α.; Sibley, L . R. In Archaeological Chemistry—III; Lambert, J . B., Ed.; Advances in Chemistry 205; American Chemical Society: Washington, D C , 1984; pp 403-424. 2. Jakes, Κ. Α.; Howard, J. H . In Historic Textile and Paper Materials, Conser vation and Characterization; Needles, H . L . ; Zeronian, S. H., Eds.; Advances in Chemistry 212; American Chemical Society: Washington, D C , 1986; pp 277-287. 3. Watson, P. J.; LeBlanc, S. Α.; Redman, C. L. Archaeological Explanation; Co lumbia University: New York, 1984; p 179. 4. Sibley, L. R.; Jakes, K. A. Clothing Text. Res. J. 1982, 1, 24-30. 5. Sibley, L. R. In Proceedings of the Twenty-Fourth International Archaeometry Symposium; Olin, J . ; Blackman, J . , Eds.; Smithsonian Institution: Washington, D C , 1986; pp 153-163. 6. Jakes, Κ. Α.; Sibley, L. R. In Proceedings of the Application of Science in Examination of Works of Arts; England, P.; Van Zelst, L . , Eds.; Museum of Fine Arts: Boston, M A , 1983; pp 221-224. 7. Berry, B. Flood Plain Data: Sampling, Coding, and Storing; Agriculture Hand book 237; U.S. Department of Agriculture, Farm Economics Division and Ec onomic Research Service: Washington, D C , 1962. 8. Redman, C. L. Archaeological Sampling Strategies; Addison-Wesley: Phillipines, 1974; 134. 9. Reid, J . J.; Schiffer, M . Β.; Neff, J. M. In Sampling in Archaeology; Mueller, J. W . , E d . ; University of Arizona: Tucson, 1975; pp 209-229. 10. Rootenberg, S. Am. Antiq. 1964, 30, 181-188. 11. Cowgill, G. L . Am. Antiq. 1964, 29, 467-473. 12. Pollnac, R. B.; Rowlett, R. M. In Experimental Archaeology; Ingersoll, D . ; Yellen, J. E . ; Macdonald, W ., Eds.c/olumbia University: New York, 1977; pp 167-190. 13. Christenson, A. L.; Read, D. W. Am. Antiq. 1977, 42, 163-179. 14. Benfer, R. A. In Sampling in Archaeology; Mueller, J. W . ; E d . ; University of Arizona: Tucson, 1975; pp 170-191. 15. Mueller, J. W. In Sampling in Archaeology; Mueller, J. W., Ed.; University of Arizona: Tucson, 1975; pp 33-43. 16. Emery, I. The Primary Structures of Fabrics: An Illustrated Classification; The Textile Museum: Washington, D C , 1966. 17. Burnham, H . B. Centre International d'Etudes des Textiles Anciens, Lyons. Bull. Liaison 1965, 22, 25-45. RECEIVED

for review June 11, 1987. ACCEPTED revised manuscript May 6, 1988.


Photomicrography and Statistical Sampling of Pseudomorphs after

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