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*Received 4 August 2005; accepted 14 February 2006.†Correspondence should be addressed to Carl Heron (c.p.heron@bradford.ac.uk ) or to Jacques Connan (connan.jacques@wanadoo.fr).© University of Oxford, 2006

Blackwell Publishing LtdOxford, UKARCHArchaeometry0003-813X© University of Oxford, 2006XXX 2006484

ORIGINAL ARTICLE

Southern Asia’s oldest incendiary missile?T. Ali et al.

SOUTHERN ASIA’S OLDEST INCENDIARY MISSILE?*

T. ALI,

1

R. CONINGHAM,

2

J. CONNAN,

3

† I. GETHING,

2

P. ADAM,

4

D. DESSORT

3

and C. HERON

2

†

1

Department of Archaeology, University of Peshawar, Peshawar, Pakistan

2

Department of Archaeological Sciences, University of Bradford, Richmond Road, Bradford BD7 1DP, UK

3

Elf Exploration Production, Direction Technique, CSTJF, Avenue Larribau, 64018 Pau Cedex, France

4

Laboratoire de Géochimie Organique, Université Louis Pasteur, 67007 Strasbourg Cedex, France

A small burnt ball was recovered in 1995 from the basal fills of a ditch surrounding the BalaHisar, or High Fort, of Charsadda, Pakistan. Associated by Sir Mortimer Wheeler with thesiege of the ancient site by Alexander the Great in 327

BCE

, the ditch forms part of the city’sdefensive circuit. Using geochemical and microscopic techniques (X-ray diffraction,micro-FTIR, SEM and GC–MS) the ball is identified as an artificial composite of mineral(mostly barite) and flammable resinous organic matter originating from conifers from thePodocarpaceae, Araucariaceae and Cupressaceae. The physical and chemical nature of thefind suggests that the ball was ignited in a fire, although whether this was a deliberate oraccidental occurrence is impossible to establish. The analytical data, combined with thearchaeological context of the find, leads us to evaluate whether the find represents southernAsia’s earliest incendiary missile.

KEYWORDS:

PAKISTAN, THE BALA HISAR OF CHARSADDA, ALEXANDER THE GREAT, SIR MORTIMER WHEELER, INCENDIARY MISSILE, CONIFER RESIN, DITERPENOIDS,

PODOCARPACEAE, ARAUCARIACEAE, CUPRESSACEAE, BARITE

*Received 4 August 2005; accepted 14 February 2006.© University of Oxford, 2006

INTRODUCTION

In 1863, Sir Alexander Cunningham identified the 23 m high mound known as the BalaHisar, or High Fort, of Charsadda in the North West Frontier Province as the ancient city ofPeucelaotis (Ali

et al.

1998; Fig. 1). One of the capitals of the Persian satrapy of Gandhara,Classical historians record that Peucelaotis was besieged by Hephaestion and Perdiccas in 327

bc

and, after a siege of 30 days, was sacked and its governor, Astes, killed (De Selincourt1958). Despite its historical significance, the Bala Hisar was not examined by archaeologistsuntil Sir Mortimer Wheeler conducted 6 weeks of excavations in 1958. During this time, hetested the lower levels of the site in order to date the foundation of the city, which he attributedto the sixth century

bce

, but also attempted to identify the course of its Alexandrian defences(Wheeler 1962, 10). These defences were identified in Trench Ch. III, where a ditch and ram-part complex was exposed on the eastern side of the mound. Although badly damaged,Wheeler estimated the ditch to have been 5 m wide and just over 3 m deep (Wheeler 1962,27). The ditch was backed by a 5.3 m wide rampart, which incorporated traces of a bridge andpostern gate (ibid.).

In 1995, new excavations were initiated by the Universities of Bradford and Peshawar inorder to refine Wheeler’s chronologies for the site (Ali

et al.

1998; Fig. 2). In the bottom of a

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Figure 1 A map showing the location of Charsadda in the North West Frontier Province.

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new trench (Ch. VI; Fig. 3) cut across Wheeler’s ditch a small, roughly spherical object (smallfind 1513) was recovered. The ball was recovered from a portion of the ditch cut, filled by aseries of seven layers of which the earliest, compact silty clay [80] contained small find 1513.Although Wheeler (1962) suggested that the feature dated to the fourth century

bce

, some

Figure 2 A plan of the Bala Hisar, showing the mound and the locations of trenches Ch. III and VI.

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notably early material was also recovered from the ditch’s fills, such as sherds of ‘RedBurnished Ware’, a ‘Single Holed Sickle’ of schist and sherds of ‘Rippled Rim’—more usuallylinked with the Gandharan Grave Culture (Stacul 1987). This material is probably redeposited,as indicated by the presence of sherds of ‘Indic’ carinated bowls with everted rims and ‘Indic’shallow, flat-bottomed dishes, dating to the first half of the first millennium

bce

(Vogelsang1992). Two radiocarbon samples were recovered from this feature, one from fill [73] (GrA-5247 2460

±

50

bp

) within the upper part of the ditch and one from fill [80]—the basal fill ofcut 55 (GrA-5250 1430

±

50

bp

)—both date to the middle of the first millennium

bce

, and

Figure 3 A plan of trenches Ch. III and VI.

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although these calibrated dates lend support they do not necessarily confirm Wheeler’s Alex-andrian assumptions.

The ball was initially classified as ‘carbonized’ material and fragments exported underlicense to the UK for further study. Measuring 52.7 mm in diameter and weighing 65.3 g, theball has suffered damage and deterioration, with less than 10–15% of the original surface ofthe ball remaining. This surface has retained a generally smooth, almost gloss-like appearance,which in places exhibits a number of fine, soil-filled, cracks and striations (Fig. 4). Theremainder of the surface displays considerable fracturing, some of which is conchoidal innature. The ball is hard, yet very brittle, and picks up an electrostatic charge. Initial sugges-tions focused on a bituminous origin. Indeed, bituminous balls have been excavated andanalysed from several archaeological sites in the Near East; for example, at Tell el’Oueili(Connan 1988; Connan

et al.

1996) in Mesopotamia and at Qal’at al-Bahrain in the Gulf(Højlund 1994; Connan

et al.

1998).

RESULTS

Two samples were taken for analysis. Sample 1151, a black lump from the charred surface,was isolated by flaking the brittle material with stainless steel tweezers over a 3 mm area.Sample 1152, a yellow resin-like material observed under a binocular microscope, wasremoved with a Dremel drill and cutting wheel at a depth of 2 mm immediately below thecharred surface. Both samples show similar elemental composition (Table 1) with 46% organiccarbon, 22% oxygen, 4% sulphur and low levels of nitrogen (0.05%). Elemental analysis doesnot fit the classical values obtained for bitumen; atomic H/C and N/C ratios are both higher inbitumen, with values of 1.2–1.3 and 0.05–0.1 instead of 0.7 and 0.0009, respectively. Moder-ate amounts of TOC (46% by weight; Table 1) coupled with 27% ash indicate that the organicmatter is not pure but probably diluted with mineral filler. X-ray diffraction, micro-FTIR ana-lysis and SEM combined with X-ray analysis has established that the organic material is mixedwith barite, quartz, calcite and strontianite (SrCO

3

). Furthermore, petrographic study and SEManalysis detected barite distributed over all the surfaces under investigation. This indicates thatfinely ground barite powder was intimately mixed with the organic matter (Fig. 5). Baritecomprises a large percentage of the mineral fraction, estimated to be around 75%. The

δ

34

Svalue of the extracted samples by chloroform is +3.0‰/CDT, which suggests that the baritemay be of hydrothermal origin. Such a geological origin is consistent with the occurrence of

Figure 4 A drawing of small find no. 1513. The ball is approximately 52.7 mm in diameter and weighs 65.3 g.

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Figure 5 A study of the mineral fillers (sample 1151) using scanning electron microscopy (SEM) with and X-ray analyser: (b) shows vacuolar structures in the mixture with numerous gas bubbles; (a), (c), (d) and ( f) represent the corresponding maps for the elements barium (Ba), sulphur (S), carbon (C) and aluminium (Al), respectively; (e) indicates the elements identified, with carbon, barium and sulphur predominating.

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Table 1

Results of the elemental and isotopic analysis on whole samples, extracted residues and chloroform extracts

Elf number

Laboratory number

Type of sample

Melting point (

°

C)

Elemental analysis Isotopic data on chloroform extracted samples

Isotopic data on chloroform extract,

δ

13

C (‰/PDB)

C% H% N% O% S% Ash% H/C O/C S/C N/C

δ

13

C (‰/PDB)

δ

D (‰/SMOW)

δ

34

S (‰/CDT)

1151 B96440 Black lump >400 46.12 2.97 0.05 21.96 4.41 26.4 0.77 0.36 0.036 0.0009

−

28.7 44.0 3.4

−

28.71152 B96441 Yellow resin >400 45.91 3.13 0.05 22.25 3.76 27.9 0.81 0.36 0.031 0.0009

−

28.9 58.0 3.6

−

28.9

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other hydrothermal minerals; namely, strontianite and siderite. Barite is currently mined inPakistan from two considerable deposits; Kalat in Baluchistan and near Rawalpindi, about 130km from Charsadda. This latter deposit is perhaps the most likely source for the barite in theball.

All surface areas examined from both samples 1151 and 1152 exhibit numerous gas bubbles(Figs 5 and 6), 10–50

µ

m in diameter, generated by the mild thermal decomposition oforganic matter or degassing of the sample upon heating. The petrographic examination ofsample 1152 under reflected and fluorescent light reveals a resin-like aspect without anyreflectance and a yellow-to-green fluorescence (Figs 6 (a) and 6 (b)). This material has notbeen subject to any carbonization process; consequently, any thermal treatment involved duringthe preparation of the ball has been very mild. The same methods, applied to the charredsample (no. 1151; Figs 6 (c) and 6 (d)), confirm the intense thermal degradation of the outersurface layer, with reflectance as high as 1%. Micro-FTIR analysis of sample 1152 byreference to two typical bitumens shows that the organic matter is very rich in oxygenatedfunctionalities, namely OH and C=O, and rather devoid of aliphatic CH groups. The IR datacorroborates the H/C ratios of 0.7 and hydrogen indices (HI; Table 2) of 200 mg hydrocarbonsper gram of the total organic carbon (TOC). Obviously, the organic material is not a bitumen,for it exhibits molecular similarities with vegetal products where OH and C=O groups arepredominant.

Geochemical data (especially Rock-Eval) confirm the absence of bitumen (see the typicalpyrogram of a bitumen from Kosak Shamali in Table 2; Connan and Nishiaki 2003) in thesamples. S2 pyrograms are unusual and peak at a high temperature (

T

max

= 457

−

465

°

C; Table 2).The high temperature of the S2 peak matches the high temperature recorded for the meltingpoints (>400

°

C). The organic matter seems to be highly polymerized. In comparison, archae-ological bitumens (Connan and Deschesne 1996), fresh conifer (pine, cedar, cypress) resins,archaeological frankincense and balms of Egyptian mummies give 420–430

°

C, 380–435

°

C,330–400

°

C and 417–430

°

C, respectively, but no values as high as 465

°

C. This very high

T

max

means that the organic matter is thermally stable despite its obvious uncharred state in sample1152. No major changes are seen in gross composition and the properties of the organic matterand its chloroform extract (Tables 1 and 2). Indeed, carbonization has only affected the super-ficial outer layer of the ball without modifying the bulk characteristics. The high temperaturesreached through ignition entailed a degassing of the pristine material in the heart of the balland formation of pyrolytic aromatics within the outer layer at the surface. The ball started toburn but combustion ceased quickly, ensuring its survival.

As expected, the extractable organic matter represents only 0.4% of the whole samples. Theso-called ‘C

15+

saturates’ and ‘C

15+

aromatics’ fractions are, respectively, less than 1% and 20%in both samples. Computerized GC–MS analysis of the ‘C

15+

alkanes’ fraction shows a com-plex mixture comprising molecules with 270, 272 (predominant) and 274 molecular ions(Fig. 7). These compounds are C

20

diterpenoids with six, five and four unsaturations. All thecompounds possess an intense

m

/

z

43 fragment, indicative of the occurrence of a propyl orisopropyl group. The most abundant of the diterpenoids has a prominent molecular ion at

m

/

z

272, together with an M-15 peak at

m

/

z

257. The base peak of this component is at

m

/

z

229.These unusual molecules are monenes, dienes and trienes of tricyclic diterpenoids, withmolecular structures close to a kaurene skeleton. Some mass spectra found in the ‘C

15+

saturates’fraction are very close to published spectra of isophyllocladene, phyllocladene and kaur-16-ene (Philp 1985). The high molecular weight compounds (406–408) suggest dienes andtrienes of C

30

triterpenoids. Computerized GC–MS of the ‘C

15+

aromatics’ of both samples

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shows a very unusual pattern, dominated by simple C2-(2,6-dimethyl-), C3-(2,4,6-trimethyl-or 2-ethyl-5-methyl-, 2-isopropyl-5-methyl = thymol) and C4-(2-ethyl-4,5-dimethyl-)phenols.These compounds occur in conifers (2,6-dimethylphenol) and essential oils (thymol). Thecharred sample from the outer layer contains the same phenols (Fig. 8), but in addition atypical pyrolytic signature comprising phenanthrene, methyl-phenanthrenes and anthracenes;benzofluoranthene is identified unequivocally. This ‘C

15+

aromatic fraction’ does not contain

Figure 6 Samples 1152 and 1151 examined under fluorescent light (a and c) and reflected white light (b and d). Sample 1152 shows a green to yellow fluorescence (λmax at 550 nm) and no reflectance. The resin-like substance exhibits a highly vacuolar appearance (gas bubbles with variable sizes up to 250 µm). Sample 1151 exhibits a yellow fluorescence (λmax at 618 nm) and an average reflectance of 1%.

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Table 2 Rock-Eval data (pyrograms of samples 1151 and 1152 and parameters determined) and the gross composition of chloroform extracts: S1 and S2 are expressedin mg hydrocarbons/g sample, S3 in mg CO2/g sample, HI in mg hydrocarbons/g total organic carbon (TOC), OI in mg CO2/g TOC and Tmax in °C

Elf number

Laboratory number

Type of sample

Archaeological reference

Rock-Eval data Chloroform extract

(%/sample)

Gross composition of chloroform extract

S1 S2 S3 TOC HI OI Tmax % sat. % aro % pol.

1151 B96440 Black lump Ch.VI-1513–80 1.5 104 10.9 51.4 202 21 465 0.4651 0.8 19.7 79.51152 B96441 Yellow resin Ch.VI-1513–80 0.5 89.5 9.5 46.0 194 21 457 0.4264 0.4 18.4 81.2

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any aromatized tricyclic diterpenoids such as retene or dehydroabietane, found in thermallydegraded conifer resins. In addition, no diterpenoid acids and related molecules with anabietane skeleton were identified in the polar fractions after diazomethane treatment.

In summary, the yellow highly polymerized material is very likely a resin-like exudate, butthe tree(s) that produced it remains unknown. The diterpenoids are not abietic derivatives, butmore likely structures with kaurane and phyllocladane skeletons. As a result, it is likely thatthe resin originates from conifers belonging to the Podocarpaceae, Araucariaceae and Cupres-saceae families (Peters and Moldowan 1993). The occurrence of both diterpenoids and triter-penoids supports the mixing of substances from more than a single plant source. We suggestthat the ball was prepared by mixing a finely ground barite with a resinous material and then

Figure 7 GC–MS (total ion current) analysis of the ‘C15+alkane’ and ‘C15+aromatic’ fractions, showing the main groups of molecular structures identified in sample 1152.

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pressed into a spherical shape. The high degree of polymerization could be due to the use ofa natural resin comprising a significant insoluble polymeric component. Alternatively, theorganic matter polymerized following ignition or long-term deterioration and weathering tobecome the hard infusible ball found at excavation.

DISCUSSION

The ball is identified as an artificial composite of mineral (mostly barite) and flammableresinous organic substances from plants. The analytical data suggest that the ball was ignited,

Figure 8 GC–MS (total ion current) analysis of the ‘C15+aromatic’ fractions: a comparison of the unaltered sample (no. 1152) with the charred one (no. 1151).

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although whether this was a deliberate or accidental occurrence is impossible to establish. Thehigh temperatures reached through ignition entailed a degassing of the pristine material in theheart of the ball and formation of pyrolytic aromatics within the outer layer at the surface.Ignition of the ball, and its recovery from a defensive ditch at the site, lead us to considerwhether the ball could have served as an incendiary missile. The ball started to burn but com-bustion ceased quickly, ensuring its survival.

Suitable parallels in terms of similar finds are not plentiful. Whilst the function of thebitumen balls described above is not known, spherical objects in terracotta or stone are well-known throughout southern Asia, ranging from the Bronze Age to historical times, and theconsensus is that they represent sling-balls (Narain 1977; Allchin 1986; Ghosh 1989). Holleyhas reconstructed the use of artillery at Masada from the analysis of stone ballistae balls(Holley 1994). Unlike small find no. 1513, none of these objects would have had incendiaryproperties. There is a wealth of documentary evidence for incendiary substances, including thephenomenon of ‘Greek Fire’ referred to in Islamic and Byzantine sources and examined bymany authors, including Partington (1960), Forbes (1964), Davidson (1973) and others. Morerecently, Mayor (2003) has reviewed this and other evidence in her overview of biological andchemical agents used in warfare in the ancient world.

Numerous textual sources refer to a range of incendiary substances and technologies, fromburning arrows to more sophisticated devices. Herodotus, for example, records that the Persianarmy set light to the wooden walls of the Athenian Acropolis during its invasion of 480–479bce, using burning hemp or flax attached to arrows (De Selincourt 1954). Similarly, Thucy-dides records that when siege engines failed to take the city of Plataea in 429–428 bce, thePeloponnesian allies burned the city by adding pitch and sulphur to bundles of wood next tothe wall. Ignition of the bundles produced such a conflagration as had never been seen before(Warner 1954). Incendiary missiles of sulphur and bitumen are recorded by Arrian ashaving been used by both Macedonians and Persians during Alexander’s 7 month siege of theMediterranean port of Tyre (De Selincourt 1958). Indeed, studies of the technical developmentof siege artillery, culminating in the use of the torsion catapult to project boulders of 40 kgsome 500 m, have drawn heavily from such sources (Marsden 1969, 1971; Cotterell andKamminga 1990).

The use of inflammable substances such as resins or their heated derivatives (tar or pitch)together with sulphur and natural bituminous substances is repeated in many sources (Mayor2003). The Arthashastra, written in or after the fourth century bce, refers to ‘small balls’ thatcould be hurled at the enemy, together with fire arrows (Mayor 2003, 233). Aeneas the Tacti-cian, writing in the fourth century bce, advised that unlit fuel, which was then ignited using afire arrow or burning pot, could be thrown at the enemy (Mayor 2003, 239). It is plausible thatflammable balls were thrown into fires already started by other means to lend fuel to theflames. In comparison with these sources, physical evidence is extremely limited, more so if thefourth century bce Lycian genre of siege scenes depicted on rock-cut tombs and sarcophagi inwestern Asia are excluded (Childs 1978). James (1983) has reviewed archaeological anddocumentary evidence of ‘fire arrows’ of Roman date. Summarizing the literary sources,James points out that the sources agree that the special iron head employed consisted of apoint and socket or tang connected by a number of bars, each bowed outwards to produce aspindle-shaped cage which would hold the inflammable material (James 1983, 142). From themedieval period, aeolipiles, or grenades consisting of ‘spheroconic’ ceramic vessels filled witha distilled mixture of resin or oil, asphalt and lime, have been identified by Pentz (1988) asforming a continuity with Byzantine ‘Greek Fire’, although others have suggested that they

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were containers of beer, wine, mercury or perfume (Ghouchani and Adle 1992). Perhaps smallfind no. 1513, now stored in the museum of the University of Peshawar, extends this continuityand may be southern Asia’s oldest example of an incendiary missile.

CONCLUSION

Geochemical and microscopic analysis of the ball confirms it as an artificial composite ofmineral (mostly barite) and flammable resinous organic matter derived from a plant source. Allevidence points to the ignition of the ball in a fire, although combustion appears to haveceased quickly, ensuring its survival. Its recovery in the basal layer of a defensive ditch atCharsadda led us to consider whether the ball served as an incendiary missile. It is not possibleto establish whether the ball was burned accidentally or deliberately.

ACKNOWLEDGEMENTS

We are grateful to the following funding bodies for their support of the Charsadda (Pakistan)Project: the Ancient India and Iran Trust, the British Academy, the McDonald Institute forArchaeological Research, Cambridge, the Stein–Arnold Fund and the Society for South AsianStudies. We are indebted to J.-L. Faggionato for the petrological study of the samples underreflected and fluorescent light, to O. Ruau for the micro-FTIR study, to J.-P. Tricard and F.Tempère for the SEM analysis and to B. Simoneit for his comments on the mass spectra of thechromatographic fractions. The ball was drawn by J. Sygrave.

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