Harris Matrix - Tool for Comprehending the Archaeological Past

Recording the Details of Archaeological Site Chronology

Stratigraphy at a 12th building at 1 Poultry, City of London. Scale is 20 cm.
Stratigraphy at a 12th building at 1 Poultry, City of London. Scale is 20 cm. Museum of London Archaeology / Getty Images

The Harris Matrix (or Harris-Winchester matrix) is a tool developed between 1969-1973 by Bermudian archaeologist Edward Cecil Harris to assist in the examination and interpretation of the stratigraphy of archaeological sites. The Harris matrix is specifically for the identification of both natural and cultural events which make up a site's history.

The construction process of a Harris matrix compels the user to classify the various deposits in an archaeological site as representing events in the lifecycle of that site.

A completed Harris Matrix is a schematic that clearly illustrates the history of an archaeological site, based on the archaeologist's interpretation of the stratigraphy seen in the excavations.

What is the History of an Archaeological Site?

All archaeological sites are palimpsests, that is to say, the end result of a series of events, including cultural events (a house was built, a storage pit was dug, a field was planted, the house was abandoned or torn down) and natural events (a flood or volcanic eruption covered the site, the house burned down, organic materials decayed). When the archaeologist walks onto a site, evidence of all those events is there in some form. The archaeologist's job is to identify and record the evidence from those events if the site and its components are to be understood. In turn, that documentation provides a guide to the context of the artifacts found at the site.

What I mean by context (discussed in detail elsewhere) is that artifacts recovered from the site mean something different if they are found in the construction foundations of the house rather than in the burned basement. If a potsherd was found within a foundation trench, it predates the use of the house; if it was found in the basement, perhaps only physically a few centimeters away from the foundation trench and maybe at the same level, it postdates the construction and may be in fact from after the house was abandoned.

Using a Harris matrix allows you to order the chronology of a site, and to tie a particular context to a particular event.

Classifying Stratigraphic Units to Context

Archaeological sites are typically dug in square excavation units, and in levels, whether arbitrary (in 5 or 10 cm [2-4 inch] levels) or (if possible) natural levels, following the visible deposit lines. Information about every level that is excavated is recorded, including depth below surface and volume of soil excavated; artifacts recovered (which could include microscopic plant remains discovered in the laboratory); soil type, color and texture; and many other things as well.

By identifying the contexts of a site, the archaeologist can assign Level 12 in excavation unit 36N-10E to the foundation trench, and Level 12 in excavation unit 36N-9E to the context within the basement.

Harris' Categories

Harris recognized three types of relationships between units--by which he meant groups of levels which share the same context:

  • a) units which have no direct stratigraphic correlation
  • b) units which are in superposition
  • c) units which are correlated as parts of a once-whole deposit or feature

The matrix also requires that you identify characteristics of those units:

  • a) units which are positive; that is to say, those that represent the upbuild of material to a site
  • b) negative units; units such as pits or foundation trenches which involved the removal of soil
  • c) interfaces between those units

History of the Harris Matrix

Harris invented his matrix in the late 1960s and early 1970s during post-excavation analysis of site records from the 1960s excavation at Winchester, Hampshire in the UK. His first publication was in June 1979, the first edition of The Principles of Archaeological Stratigraphy.

Originally designed for use on urban historic sites (which stratigraphy tends to be horrendously complex and jumbled), the Harris Matrix is applicable to any archaeological site and has also been used to document changes in historical architecture and rock art.

Although there are some commercial software programs that assist in building a Harris matrix, Harris himself used no special tools other than a piece of plain gridded paper--a Microsoft Excel sheet would work just as well.

Harris matrices may be compiled in the field as the archaeologist is recording the stratigraphy in her field notes, or in the laboratory, working from notes, photos and maps.

Sources

This article is part of the About.com guide to something or other, and part of the Dictionary of Archaeology

The best source for information about the Harris Matrix is the Harris Matrix project website; a recent software program is available known as the Harris Matrix Composer which looks promising, although I have not tried it out so can't tell you how well it works.

There is a terrific vimeo available which illustrates how to construct a matrix using a white board.