Hannibal's Engineers and Livy (XXI.36-7) on Burned Rock - Truth or Legend?
Many have commented on Livy's famous passage (Hist. XXI.36-7) where he describes Hannibal's engineers surmounting a large rock blockage on the Italian descent of the Alps, including the late great French archaeologist Serge Lancel (Lancel, 1998:78-9) and our History Channel team 2006 production (June-November, 2006). According to Livy, and repeated in Ammianus Marcellinus (de Sanctis, 1917:77 ff), the ancient engineers poured boiling vinegar on the rocks to facilitate their massive cracking along with burning the rocks by a fire underneath them, after which they were able to remove sufficient rock to pass by. One immediate problem with this story - as Lancel affirmed - is that it is not repeated in Polybius, the more credible source, who also describes Hannibal's engineers removing blocked rock after an avalanche (Polybius, Hist. III.54.5-55.1) but without this colorful detail of vinegar and burning rock. Polybius is so trustworthy on topographic detail it is surprising his text has such a lacuna if the story is true.
But the story is not without substance for several reasons. First, armies often carried wine for both drinking consumption and secondary medical or pain-relieving purposes, and wine traveling in the ancient world often easily turned to vinegar. Second, like many acids including low concentration hydrochloric acid used by field geologists everywhere, vinegar (acetic acid) reacts on carbonate rock, which can effervesce or even dissolve under acid applications, and this effect would be accelerated with the application of heat that would itself cause the rock to expand too rapidly and possibly split, especially because this rock was very cold to begin with in early winter when snow had already fallen in the pass. Applying the different coefficients for vinegar and rock of thermal expansion and contraction, if the vinegar penetrated the rock, the rock's own thermal expansion by the heating and compounded by the added expansion of the vinegar converting to steam inside the rock could easily cause the rock to shatter in massive exfoliations, but also expanding greatly because the rock was also being heated from the fire below. This differential of thermal contraction and expansion and reaction to boiling vinegar and heating and burning by fire would also work similarly on silicate rock or low grade metamorphic schists, but most likely to a lesser extent depending on mineral content and initial friabilty. Because the treeline was likely higher in 218 BCE due to warmer climate - what is known as the RWP or Roman Warm Period by paleoclimatologists (Hohlhauser, Magny and Zumbuhl, 2005) - and because ancient armies carried embers for nightly cooking fires, providing both fuel timber from the western (now French) ascent and adequate fire-starting materials would have been fairly easy, as discussed in our 2006 History Channel production. Third, our Stanford Alpine Archaeology teams have identified several such possible contexts on the Clapier descent into Italy in 1996, 2004 and 2006, awaiting scientific confirmation this summer. The avalanche locus and potential ancient carbonization and its dating has also been described elsewhere by this author, including at the Roman Archaeology Conference-Theoretical Roman Archaeology Conference in London in March, 2007 (Hunt, 2007b) and prior lectures at Stanford University. Radiocarbon dating is just one possible method to date carbonized stone; others include stone weathering processes delineated by this author elsewhere (Hunt, 1991:253 ff) and include lichenology studies (Hunt, 2007a:15-6). Nonetheless, the problem is exacerbated by the fact that our team has found not just one but several potential carbonized loci considerably far apart. Lichen growth in some of these alpine contexts is enriched by the ash there. The story is typically enhanced by Livy's colorful detail, which may or may not be true, or enhanced by borrowing from other sources. Nonetheless, when one views the Clapier descent and the rock blockages and avalanches that have taken place there over millennia that our team has long documented, such Alpine blockages are not at all unreasonable, however addressed by Hannibal's army engineers wherever this could have happened as described by his ancient sources.
copyright © 2007 Patrick Hunt
The History Channel series broadcast, "Engineering an Empire: Carthage", was produced at KPITV, New York and filmed in various other locations, in June, 2006 and aired in November, 2006. Patrick Hunt was one of the featured scholars.
Hanspeter Hohlhauser, Michel Magny and Heinz Zumbuhl. "Glacier and lake-level variations in west-Central Europe over the last 3500 years" The Holocene 15.6 (2005) 789-801.
Patrick Hunt. Provenance, Weathering and Technology of Selected Archaeological Basalts and Andesites. Ph.D. Dissertation, Institute of Archaeology, UCL, University of London, 1991. Chapter 8, 253-98.
Patrick Hunt. Alpine Archaeology. New York: Ariel Books, 2007a.
Patrick Hunt. RAC-TRAC Abstracts, London University College London, March 2007b. Seventh Roman Archaeology Conference and Seventeenth Theoretical Roman Archaeology Conference, March 29-April 1, 2007, pp. 17-18.
Serge Lancel. Hannibal. London: Blackwells, 1998 (previously in French and released in Paris, 1995).
Gaetano de Sanctis. Storia de Romani. Torino, 1917, vols. III.2 & IV.1, 77 ff.
The author was a graduate student intern at the Radiocarbon Lab of USGS, Menlo Park in the late 1980's under Dr. Stephen Robinson.
Photo credit: This is not a photo of a Clapier context described above for reasons of protecting intellectual property, but is instead a generic Alps photo, courtesy of www.transalpriders.com