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Chapter Ten: Patterning in Earthen Fortifications
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ChaptEr tEn Patterning in Earthen Fortifications lawrEnCE E. babits introduCtion Earthen fortifications have been utilized for centuries. Anglo-Americans can look to the defenses at Maiden Castle, the Antonine Wall, Offa’s Dyke, and the English Civil War for ancestors of pre-1865 American works, albeit with later French influence. More recent examples can be found in World War I trench lines and dugouts, hundreds of foxholes dug by Allied and Axis troops across Europe, U.S.-built firebases in Vietnam , and the 1990–91 “berm” along the Saudi border built by the Iraqis. This chapter provides a synthesis of the earlier earthen fortifications, a look at how they were built, and some things an archaeologist should look for when excavating. Although most earthworks are seen as temporary, many fortifications constructed in the past obviously had some permanence, because their footprint is still evident on the landscape today. This paper will concentrate on the 1750–1865 era but the terms, methods, and results are virtually the same from 1600 to 2000. Hence, American Civil War photographs provide a valid starting point for accurate imagery to supplant what exists today. From the photographs, it will be obvious that the longer a military force was on-site, the more elaborate the fortifications could be. invEstiGatinG Earthworks Any investigation of earthen fortifications should start with the technical manuals of the day. Understanding what was intended and comparing the ideal to actual fieldworks allows better interpretation of the often complex structures. Using the proper, period terminology is also important. Many terms utilized in the manuals have very specific meanings that convey a great deal of information. For example, the meaning of the word “berm,” has changed from “a flat space above the scarp” in the eighteenth century, to “an earthen wall” in the twentieth century. There is a key difference between palisade and stockade that relates to gaps between the vertical logs of a palisade, spaces that are not found in a stockade. The glossary, using original text, included in this volume should provide clarification. Knowledge of local history relative to the site is important. This information can be gleaned from residents , county and town histories, maps, photographs, and paintings. Finally, as Balicki (chap. 6) points out, an archaeologist should never overlook local collectors who often have great knowledge and cultural material specifically related to their locality. A visual inspection, including map, aerial photographic and terrain analyses can be particularly useful . Crop marks are zones where growth is greener or taller due to disturbed soil, and/or more water and nutrients. The location of such differences can provide clues to subsurface fortification elements. Even in heavily wooded areas, the growth of trees on rectangular or linear mounds can cause shadows that reveal trench and mound lines. Visible remains can include depressions that were once fort ditches, magazines, and bombproofs (Babits 1990). On mounds, a depression can often be a clue to an internal structure. Although it is not often done, a geological study of the area should be undertaken. The underlying strata can provide key information about the site, indicating 114 lawrence e. babits why fortifications were successful, or why they were not. An outstanding example of what geology can reveal about fortifications is Doyle’s (1998) study of the World War I Western Front. Coupled with the geology , an understanding of the drainage is also essential. Ed Rutsch (personal communication) was fond of saying, “If you understand a fort’s drainage, you understand how the fort was built.” During the American Civil War, many fortifications were built on prehistoric shell middens because they were on well-drained soil. Various forms of remote sensing can be helpful (see Hanna, chap. 2). Ground-penetrating radar (GPR) can be useful on sites suspected of having buried fortifications, but “ground-truthing” by excavation will still be required to verify the nature of any anomaly that is observed. Resistivity surveys are time consuming but may well show outlines of buried works because the different soils interrupt electrical currents. A magnetometer that measures variations in the magnetism of the earth might be useful, particularly if large amounts of iron metal are present. Metal detectors can be very useful, but, as Balicki and others in this volume point out, their utility depends on the experience of the operator and the quality of the machine itself Excavation of earthwork features should be designed to minimize damage to the archaeological resource, while still recovering a maximum of meaningful information . Following historical research...