archaeology of a naval battleﬁeld: h. l. hunley and uss … · 2013-01-31 · modern naval...

The International Journal of Nautical Archaeology

(2006)

35

.1: 20–40doi: 10.1111/j.1095-9270.2006.00089.x

© 2006 The Authors. Journal Compilation © 2006 The Nautical Archaeology Society.Published by Blackwell Publishing Ltd. 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA.

Blackwell Publishing LtdD. L. CONLIN & M. A. RUSSELL: ARCHAEOLOGY OF A NAVAL BATTLEFIELDNAUTICAL ARCHAEOLOGY, 31.2

Archaeology of a Naval Battlefield:

H. L. Hunley

and USS

Housatonic

David L. Conlin and Matthew A. Russell

National Park Service, Submerged Resources Center, 2968 Rodeo Park Drive West, Santa Fe, NM 87505, USA

The American Civil War shipwrecks

H. L. Hunley

and USS

Housatonic

have been the focus of intensive archaeologicalinvestigations since the discovery of

Hunley

in 1995.

H. L. Hunley

, the world’s first successful combat submarine, sank theUnion blockader USS

Housatonic

in 1864, but sank immediately afterwards. In work done prior to the recovery of

Hunley

in2000, site-formation processes for both vessels were a primary research focus—a necessary precursor to identifying battlefieldbehaviour. This paper presents research on the

Hunley

/

Housatonic

Naval Engagement Site, where both wrecks are treated ascomplementary components of a single battlefield site.

© 2006 The Authors

Key words:

Submarine, American Civil War, battlefield archaeology, site-formation processes.

T

he American Civil War shipwrecks

H. L.Hunley

and USS

Housatonic

have beenthe focus of intensive archaeological

investigations since the discovery of

H. L. Hunley

in 1995.

Hunley

, the world’s first submarinesuccessful in combat, attacked and sank theUnion blockade ship USS

Housatonic

in February1864, but sank immediately afterwards. This paperpresents objectives, research and results of fieldinvestigations conducted between 1996 and 1999on what the authors term the

H. L. Hunley

/USS

Housatonic

Naval Engagement Site. Researchersconsidered both wrecks as complementarycomponents of a single archaeological site, abattlefield affected by similar cultural and naturalprocesses. A series of projects initiated before

Hunley

’s recovery in 2000 gathered maximuminformation from minimum impact to thearchaeological resources. This article will notdiscuss the archaeology and technical aspectsof

Hunley

’s recovery in August 2000. Projectprincipals from the United States Navy’s NavalHistorical Center (NHC), National ParkService’s Submerged Resources Center (SRC) andSouth Carolina Institute of Archaeology andAnthropology (SCIAA) planned and conducteda series of investigations that were multi-disciplinary and science-based. In 1996, initial

investigation of

H. L. Hunley

sought to verify theidentity of the wreck as the ill-fated submarineand assess its condition and state of preservation(Murphy, 1998). As a follow-up to the 1996

Hunley

assessment, an extensive field projectwas conducted in 1999 to evaluate

Housatonic

’sremains and their archaeological potential(Conlin, 2005). In both cases, site-formationprocesses were a primary focus of investigation.Beyond specific questions answered about eachwreck, the multi-component site was analysed asa naval battlefield, following the theoretical andmethodological research orientation pioneered atthe Battle of the Little Bighorn (Scott and Fox,1987).

Historical context

On the evening of 17 February 1864, the tinyConfederate submarine

H. L. Hunley

, under thecommand of Lieutenant George Dixon, slippedfrom its dock at Breach Inlet on the outskirtsof Charleston, South Carolina, and began itshistoric voyage to attack the Union blockade.Almost three hours later, under a bright moonand in calm seas, the submarine and its crew ofeight rammed a 60 kg (135 lb) black-powdercharge into the side of the Union blockade ship

D. L. CONLIN & M. A. RUSSELL: ARCHAEOLOGY OF A NAVAL BATTLEFIELD

© 2006 The Authors. Journal Compilation © 2006 The Nautical Archaeology Society 21

USS

Housatonic.

Backing away,

Hunley

tripped alanyard and detonated the charge. As pieces of

Housatonic

’s decking blew high into the nightsky,

Hunley

disappeared and remained lost for131 years. The world’s first successful submarineattack had been precisely planned andsuccessfully executed by the Confederate Statesof America.

The American Civil War was, with the possibleexception of the Crimean War, the first conflict inwhich both sides reaped the dubious benefits ofthe Industrial Revolution. Faced with the North’soverwhelming industrial capacity, the Southsought an advantage through application oftactical and technological ingenuity. In broadterms, Confederate naval actions took bothoffensive and defensive forms. Offensively,unable to build a fleet to match the Union,the Confederacy focused its efforts on theconstruction of fast, well-armed, technologically-sophisticated commerce raiders such as CSS

Alabama

and CSS

Florida

to carry out a

guerrede course

against Union shipping worldwide.Defensively, the South’s principal concerns werebreaking the blockade to maintain internationalcommerce and defending its ports. For harbourdefence, the Confederacy turned to the relativelycheap but effective use of torpedoes (mines) andthe construction of ironclads such as CSS

Virginia

and CSS

Palmetto State

. The South also had asmall but vigorous program of innovative newtechnologies used for offensive operations againstthe blockade—notably the semi-submersibleand submersible. In short, submarine warfareduring the Civil War emerged largely as a Con-federate response to the Union blockade ofSouthern ports, and within the narrowly-structuredcontext of the blockade emerged a remarkabledrama of actions and reactions, strokes andcounterstrokes, and technological innovationsand responses that culminated dramatically innaval combat off Charleston, South Carolina inmidwinter 1864.

USS

Housatonic

and

H. L. Hunley

representtwo sides of a type of naval engagement which,50 years later, would become a regular featureof war at sea—submarine against surface ship.Writing about events two years previous to the

Hunley-Housatonic

engagement, former First SeaLord Winston Churchill noted, ‘The combat ofthe

Merrimac

and the

Monitor

made the greatestchange in sea-fighting since cannon fired bygunpowder had been mounted on ships’ (1995:398). Churchill, like most naval historians, saw

the 9 March 1862 engagement between the Unionironclad USS

Monitor

and the Confederateironclad ram CSS

Virginia

at Hampton Roadsas a pivotal moment in the development ofmodern naval technology and tactics. Thoughfew would deny that the obsolescence ofwooden warships was effectively demonstratedin Virginia that day, many fail to appreciatethat another profound development in navalwarfare—the first successful attack on asurface ship by a submarine—occurred just twoyears later in the contested waters off Charleston,South Carolina.

The era of armoured battleships peaked in thefirst half of the 20th century, but by 7 December1941 the devastation of the United States’Pacific Fleet by Japanese naval air-power atPearl Harbour, Hawaii, established the loomingstrategic irrelevance of the ironclad legacy. Incontrast to battleships, although

Hunley

’s successwas not repeated for another 50 years, theimplications of that first submarine attackcontinue to affect global geopolitics and strategicthinking today.

Archaeology of a naval battlefield

H. L. Hunley

’s attack on USS

Housatonic

produced an archaeological site with twoprincipal features, the wreck of

Hunley

andthe wreck of

Housatonic

, as well as a numberof smaller but important components. Over aseries of field projects spanning 1996 to 1999,underwater archaeologists investigated anddocumented the wrecks and associated outlyingmaterials (Murphy, 1998; Conlin, 2005). Whatresulted was the archaeology of a naval battlefieldwith both sides represented. This offered theopportunity to analyse the progression of theattack and the tactics involved by carefuldocumentation of the material remains—directlycomparable to similar archaeological studiesdone at the Mexican-American War battlefieldof Palo Alto (Haecker and Mauck, 1997), theCivil War battlefield of Monroe’s Crossroads(Scott and Hunt, 1997), and the Indian Warbattlefield of the Little Bighorn (Fox and Scott,1991; Fox, 1993).

Battlefield archaeology can give unique insightinto the anthropology of war (one of the mostpervasive aspects of human society), and canprovide data on how decisions are made in theheat of battle. Archaeological study of battlefieldsis based on the premise that warfare is:

NAUTICAL ARCHAEOLOGY,

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22 © 2006 The Authors. Journal Compilation © 2006 The Nautical Archaeology Society

... one of the most organized, premeditated, regi-mented, and patterned forms of human behavior... the actions of military units on a battlefield arebased on the tactics of the prevailing military wisdomof the day;

they are not random

. Therefore, one shouldnot expect the debris of battle to be distributedrandomly over a battlefield. The tactics employedon a battlefield do leave their traces in the archaeol-ogical record. Subsequently, if natural forces orhuman activities do not significantly disturb, mix,or mask all or parts of the battlefield, it should bepossible to identify and define artefact patternscreated by the tactical positions and movements ofindividual military units (Potter

et al

., 2000: 13, hisemphasis).

One of the first to recognize the potential forbattlefield archaeology was Snow in his 1972investigation of the American RevolutionaryWar battlefield at Saratoga (1981). Innovativemethodology allowed Snow and his studentsto identify the remains of both British andAmerican lines, fortifications and earthworks. Thismethodology was advanced by Scott and Foxin their pioneering work at the Little BighornBattlefield, where they used unique characteristics,or ‘signatures’, of different artefact classes totrace individual and unit movements across thebattlefield as the structured behaviour of thebattle unfolded (Scott

et al.

, 1989: 146–7). Duringthe archaeological study of the Battle of theLittle Bighorn, Scott

et al

. (1989: 145–50)proposed a ‘Post-Civil War Battlefield Pattern’,which traced individual movement patterns basedon artefacts bearing unique signatures, such asshell casings, and from that discerned unitpatterns, which taken as a whole represent theprogression of a battle in its entirety (this is whatScott

et al

. (1989: 148–9) refer to as ‘dynamicpatterning’). They then analysed the resultingpatterns and compared these to historicalaccounts that not only described the specificsof the battle, but more general cavalry tacticsfollowed by the US Army at the time. Thisallowed researchers to evaluate the documentedpatterns in terms of expected behaviourreferenced in historical documents, and provideda baseline for comparison to other Indian Warsbattle-sites (Scott

et al

., 1989: 150).Like their terrestrial counterparts, naval

battlefields are not rare—over the centuries thesea-floor has become littered with remains ofships lost as the world’s naval powers vied forcontrol of oceans and changing trade routes.What is less common is the archaeological study

of a naval engagement explicitly designed to learnhow the battle unfolded from an archaeologicalperspective and what that can tell us about navaltactics used by the combatants. Investigation ofthe

Hunley

/

Housatonic

Naval Engagement Sitefrom 1996 to 1999 provided the opportunityfor systematic, methodical study of the materialremains from a naval engagement with bothparticipants represented. The type of ‘dynamicpatterning’ documented by Scott

et al

. (1989:148–9) cannot at this time be easily appliedto naval engagements; however, the generalapproach to an investigation of material remainsfrom both sides of a naval engagement can allowus to identify tactics and the results of specificactions. After accounting for natural and culturalsite formation processes, damage identified on

Housatonic

’s remains can be directly attributed to

Hunley

’s attack. Based on these observations,naval tactics can be hypothesized and historicalaccounts correlated or refuted. This is corollaryto what Scott

et al

. refer to as ‘gross patterning’.or a static interpretation of events independent oftemporal variables (1989: 146–7).

The first step in using a battlefield approach inthe present study was to document the relativeposition, orientation, spatial organization andlevel of integrity of both major site components.Next, taphonomic processes were identified andcontrolled for—this was especially significantfor

Housatonic

’s remains because we could notisolate and recognize potential battle damageinflicted by

Hunley

until we understood theconsiderable natural and cultural formationprocesses that created the site in its present form.Finally, we could compare archaeological datato historical documents to confirm or refutespecific events documented by participants andobservers during the course of the battle. Anotherimportant site component was also documentedduring this project: a large iron buoy thatprobably marked

Housatonic

’s wreck as anavigational hazard for many decades after theCivil War. Although not directly related to thebattle, the buoy is part of the complex humaninteractions that produced the site as a whole.

Project background

On 3 May 1995 archaeologists sponsored byauthor Clive Cussler’s National Underwater &Marine Agency (NUMA) successfully locatedthe wreck of

H. L. Hunley

6.4 km (4 miles) offthe coast of Charleston, South Carolina, using a



combination of magnetometer survey and testexcavation (Fig. 1) (Hall and Wilbanks, 1995).In 1996, at the request of the Naval HistoricalCenter, the National Park Service’s SubmergedResources Center, the South Carolina Instituteof Archaeology and Anthropology, and arch-aeologists from the NHC, returned to co-ordinates furnished by Cussler’s team to confirmthe identity of the object located as the wreck of

H. L. Hunley

; to assess the wreck’s conditionand document the site to the extent conditionspermitted; and to evaluate the feasibility ofexcavation and recovery of the vessel remainsbased upon scientific study of the site and itssurroundings (Lenihan and Murphy, 1998: 15;Neyland and Amer, 1998: 12). Following the1996 assessment, which recommended

Hunley

’srecovery as the preferred management alternative,the same agencies returned to the site in 1999 toinvestigate

Housatonic

’s remains. Goals were toevaluate the wreck’s integrity and evaluate thesite’s spatial organization, recover representativeartefacts for interpretation and, if possible,delineate battle-damage inflicted by

Hunley

.

1996

H. L. Hunley

project

Pre-disturbance survey

A comprehensive pre-disturbance remote-sensingsurvey of the area, including both the location of

the

Hunley

wreck and the historically-recorded siteof

Housatonic

, preceded

Hunley

test excavationsin 1996. Systematic remote sensing with towedinstrumentation produced a synoptic overviewof known and potential cultural remains andrelationships within the study area and was a keyfirst step in the battlefield approach (Murphy

et al.

,1998a: 45–62). This produced a comprehensivedata-set that was immediately accessible for planningand aided interpretation during excavation.The survey design was based upon the wide-areaarchaeological survey methodology developedduring the National Park Service’s SystemwideArchaeological Inventory Program (SAIP) surveyof Dry Tortugas National Park, which began in1993 (Murphy and Smith, 1995; Shope

et al

., 1995;Murphy, 1997). Remote-sensing instrumentationused for the 1996 pre-disturbance survey includeddeployment of a portable base-station to providedifferentially-corrected GPS positioning formagnetometer, side-scan sonar, survey depth-sounder, sub-bottom profiler, and RoxAnn bottomclassification device (Murphy

et al.

, 1998a: 45).Using these sensors concurrently provided amulti-parameter natural and cultural resourcehydrographic survey to address goals set forth inthe research design (Lenihan and Murphy, 1998:15). Pre-disturbance surveys are common practicein underwater archaeology, and they comprise afundamental aspect of a minimum-impact

Figure 1. Charleston, South Carolina, USA.


35

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approach, long a standard operating procedurein the National Park Service (Russell and Murphy,Murphy, 1997).

From the outset of the 1996 assessment, thewrecks of

Hunley

,

Housatonic

and associatedremains have been considered as differentcomponents of a single, multi-component site.Comprehensive remote-sensing data of the areawas incorporated into a Geographic InformationSystem (GIS) database appropriate for bothimmediate operational issues and long-termsite management. GIS, an important tool for theSRC, allowed for rapid data analysis during the1996

Hunley

project and later incorporation intopermanent South Carolina and federal archives.This approach resulted in an electronic productincorporating available digital data, such asaerial imagery and digitized historical maps withproject-specific results that allowed rapid andeasy manipulation to examine relationships thatwould otherwise be difficult to observe. The GISdata set formed the foundation for all subsequentresearch on the site and provided a standardized,permanent, cumulative, computer-accessibleproduct for multiple applications of projectresearchers, managers, and those involved inplanning and conducting future site investigations.

The 1996 high-resolution pre-disturbance surveylocated cultural materials and characterizedthe environmental context of both

Hunley

and

Housatonic

. These data were used to assistoperational and interpretive objectives. Developinga remote sensing-derived site characterizationbefore beginning test excavation was importantto ensure related features near the principalcomponents were recognized and investigated.Location of outlying ferrous masses possiblyassociated with

Hunley

, or perhaps related tothe

Hunley-Housatonic

engagement, was also anobjective (Lenihan and Murphy, 1998: 15–16;Murphy

et al.

, 1998a: 45). Outlying magneticanomalies, indicative of cultural remains, werelocated during the 1996 survey, but notinvestigated at that time.

The magnetometer data were contoured on a2-gamma (nanotesla) interval using the gradientmethod, produced by subtracting one point fromthe next and plotting results at the position of thesecond point, which produces absolute variationfrom the ambient magnetic field. This method allowscorrection for diurnal changes and facilitates thelocation of the physical object responsible for themagnetic anomaly, which experience has shown isinvariably at the point where the magnetic gradient

is the steepest (Murphy and Saltus, 1998: 360).Magnetometer survey results indicated fourmain concentrations of ferrous material withinthe survey area and several smaller (less than10-gamma) anomalies (Fig. 2). One of the mainanomalies was identified as

Hunley

, a second asthe

Housatonic

wreck site, while the third andfourth ferrous concentrations, located betweenthe other two, were unknown until they wereinvestigated in 1999.

Fieldwork

Site verification for

Hunley

relied on congruenceof key features from historical descriptions of thesubmarine. Definitive verification depended uponlocation of particular unique features includingthe forward hatch, aft hatch, snorkel-box, dive-plane, cutwater, screw, rudder features, keelballast and bow spar or fittings. Verificationwould be established if five or more of theattributes were located (Russell and Murphy,1998: 67). Because there was approximately 1 m(3 ft) of sediment above the suspected

Hunley

, thegeneral strategy was first to uncover the limitedarea disturbed by the 1995 NUMA investigationto gain excavation experience with the site’sparticular conditions and to refine excavationmethodology before removing previously-undisturbed sediments. After opening the firstexcavation unit in the forward hatch and snorkel-box area, a second excavation unit was openedtoward the vessel’s stern to locate the aft hatch;the two excavation units proceeded towardmidships to join in the middle.

To locate the first two excavation units, the vesselextremities were established with systematicmetal-detector examination, and the excavationunits located 2 to 3 m (6 to 9 ft) in from eachend of the hull. Project leaders decided thatthe potentially fragile stern area should only beexcavated once, when the vessel was ultimatelyrecovered, if that decision was made. The afterend of the submarine was left undisturbed untilthe end of the project when a narrow trenchalong the top hull centre-line was carefullyexcavated to the aft-most point of the hull toestablish accurate overall hull length. The bowand its potentially fragile spar attachments werealso avoided until the end of the project when,as in the stern, the centre-line was excavatedforward to finish overall length measurementsand determine whether any portions of the sparor spar attachments remained on the hull top(Russell and Murphy, 1998: 67–8).



Figure 2. Magnetometer data from the H. L. Hunley/USS Housatonic Naval Engagement Site, showing data points (top),full field magnetometer contours (middle) and gradient magnetometer contours (bottom).


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Key features located during the course ofthe excavation, including the forward and afthatches, cutwater forward of the forward hatch,snorkel-box, dive-plane and keel ballast, togetherconfirmed the wreck as H. L. Hunley (Murphyet al., 1998b: 76–85) (Fig. 3). Archaeologists thenfocused on mapping and documenting the exposedremains, and began the condition assessment,which primarily involved investigation of site-formation processes and a corrosion study ofHunley’s hull. Corrosion studies are not new toarchaeological evaluations of submerged metal-hulled vessels. They were conducted on theUSS Tecumseh as early as 1969, when researchersnoted heavier corrosion of rivets relative towrought iron plates (Baker et al., 1969). In situstudies have been conducted on USS Arizona(Lenihan, 1989; Russell et al., 2004) and USSMonitor (Arnold et al., 1991) in the UnitedStates; and on SS Xantho in Australia (McCarthy,2000). The goal in the case of Hunley was to deter-mine the state of preservation, and by implication,strength of the metal comprising the hull to makemanagement recommendations for long-termpreservation and possible recovery (Murphy et al.,1998c: 108).

Close examination of the entire exposed hullrevealed Hunley was encrusted with a very tough,strongly-adhering layer resistant to mechanicalimpact and abrasion. This layer was presumedto reduce hull corrosion rates significantly, as hadbeen demonstrated on other sites (North, 1976:253). Subjective observations of the investigatorswere that no areas appeared weak, and noobvious areas of differential corrosion, thinareas, or penetrations in the shell plates werepresent in the excavated areas. Overall, the hulland hatches appeared solid, relatively sound andstrong, the only observed damage being a hole inthe forward portion of the forward hatch (whichmay have been damage inflicted during theattack). At this level of investigation, based onobservations and measurements taken as part ofthe comprehensive corrosion study (Murphyet al., 1998c: 107–17), the hull appeared probablyable to withstand recovery and conservation.Because corrosion was presumably ongoing,Hunley would inevitably become fragile enoughto obviate recovery plans. Due to the potentialthreat of unauthorized removal of portions ofthe submarine because of intense public interest,recovery became the primary management

Figure 3. The Hunley site-map generated during the 1996 assessment.



recommendation instead of the more usualoption of long-term in situ preservation (Murphyet al., 1998c: 117).

As part of the 1996 assessment of Hunley,biological indicators were used to establisha burial sequence. Well-documented biologicalpioneering sequences are available for theCharleston Harbour area, and they were used toinform on post-depositional history. Examinationof hundreds of steel structures, some within 2 km(1.2 miles) of Hunley, monitored by biologists asa normal part of their artificial reef programresearch, evinces a typical pioneering sequenceon newly-introduced ferrous objects of barnaclesoccurring in a matter of months; bryozoans,hydroids and algae next; and hard coralsoccurring in 3 years. Biologists from the SouthCarolina Department of Natural Resourcesconducted a survey of Hunley’s upper hull andhatches during the 1996 documentation (Bell andMartore, 1998). At that point, only the hatches,hull top and port hull side portions wereexposed. An excavation was conducted the daybefore the biological fieldwork to facilitateexamination of the area forward of the aft hatchfrom the hull top to the keel. The biologistsexamined all exposed hull portions and collectedfive intact, complete star coral colonies(Astrangia danae) representative of observedcorals. All corals observed were located on thehull’s upper surfaces. Two samples were fromeach hatch and another from the hull top aft ofthe snorkel box. These slow-growing star corals,the most common in the region, develop in un-branched patches seldom exceeding 5 cm indiameter. Coral colony size indicates continualgrowth of 5 to 13 years for four of the colonies,with one 30 mm by 15 mm colony suggestingapproximately 10 to 20 years of uninterruptedgrowth. The biologists studied these samplesto determine whether they were sequential orcontemporary. They concluded that, basedon similar discoloration, size, and degree ofweathering, all colonies appeared to be fromapproximately the same fouling community,suggesting one period in which significant bio-fouling took place. The coral species take 2 to 3years to establish a viable colony, consequently,their absence on the lower hull portions suggeststhe lower hull was buried before these organismscould become established. The biologists’ overallconclusion was that after sinking, Hunleysubsided into the sandy sea-bed but remainedpartially exposed for perhaps 10–15 years during

which time a well-developed marine foulingcommunity was established on any exposedsurfaces. Eventually the entire vessel was buriedand probably remained so until its discovery (Belland Martore, 1998).

Another analytic procedure important toassessing Hunley in 1996 was dating sedimentsabove the hull. Radiometric dating for threehand-collected cores was conducted bymeasuring the amount of the radioisotope 210Pb(lead 210) present. This procedure was developedin the 1960s as a means to establish sedimentchronologies. In most environments, themaximum dating range for the procedure is 100to 150 years. The radioisotope 210Pb is a memberof the 238uranium decay series derived from222radon, which has a half-life of 3.8 days anddecays in the atmosphere. 210Pb, with a half-lifeof 22.26 years, is supplied to bottom sedimentsprimarily by stream run-off, where it is rapidlytransported to bottom sediments and remainschemically immobile (Martin and Rice, 1981:1–3). These characteristics provide a datingmethod that ‘has become the most importantgeochronometer for sedimentary geologist/geochemists working with samples deposited inthe last 100 years’ (Cutshall et al., 1983: 309).Procedures for dating sediments to determineaccumulation rates have been often used inmarine geology, but it has only recently beenapplied to archaeological problems. Researchersselected this dating technique because the shorthalf-life can provide a reliable indication ofthe depth of recent sediment disturbance, andseemed an ideal tool for assessing Hunley burialsequence. If the sediments were of recent origin,it would indicate that the hull was episodicallyexposed to oxygenated water, which wouldincrease corrosion rates and imply a lower levelof preservation than would a single burial event.

Researchers at the Department of GeologicalSciences, University of South Carolina,conducted radiometric analysis of three sedimentcores surrounding Hunley. They found the 210Pbcontent of two shallow cores did not diminishwith depth, which indicates coarse, well-mixed,upper-level sediments. These cores wereseparated into fine and coarse grains. A core thatwas hand-collected directly above Hunley’s hullhad depleted levels of 210Pb when compared tothe fines in the shallow cores, and like the others,these levels did not diminish with depth. Thiscore’s 210Pb content indicated it had not beendisturbed for about 100 years (Moore, 1998). The

NAUTICAL ARCHAEOLOGY, 35.1


radiometric dating results were consistent with thebiological investigation conclusions. Implicationsof radiometric sediment dating were importantto consider when evaluating results of in-situhull corrosion measurements. Indications werethat Hunley was probably in a better state ofpreservation than it would have been had itbeen subjected to frequent exposures of movingoxygenated water. Instead of assuming thehighest deterioration rate of sound metal in theshell plate, there was sufficient data to assumea rate lower in the expected range of corrosionrates for wrought iron.

Separate and convergent lines of evidenceinvestigated during the 1996 assessment indicatedthat sediments completely covered Hunley soonafter its loss, most likely within 25 years. Theevidence indicated that the vessel had notbeen periodically exposed to sea-water throughepisodic burial and reburial events. Becauseevidence supported a single burial event andcontinued burial since shortly after 1864, Hunleywas inferred to be stronger than it would havebeen if exposed, which indicated that vessel re-covery was feasible. The 1996 Hunley site assess-ment generated critical information about thesubmarine and site-formation processes followingits sinking in 1864. Hunley’s location, approxi-mately 300 m (1000 ft) from Housatonic’s wreck,corroborated testimony delivered by Union sailorsat the court of inquiry convened following theattack (Bak, 1999: App. A). A small hole in theforward hatch was thought to be damagesustained during the attack, although at presentthe submarine’s loss is not attributable to anydefinitive physical damage. While the technologyof the submarine itself was impressive, a broaderunderstanding of the historic import of theengagement between the two sides necessitated anexamination of Hunley’s victim, USS Housatonic.

1999 USS Housatonic projectThe research design for 1999 archaeologicalwork on USS Housatonic built directly upon pro-ductive research completed on Hunley in 1996.That remote-sensing survey had indicated thatthe Hunley/Housatonic Naval Engagement Siteconsisted of Hunley, Housatonic and two smalleranomalies (referred to as Third and FourthAnomalies). In addition to documenting andassessing the Housatonic site, another objectiveof 1999 fieldwork was to identify and documentthese two elements. Research in 1999 focused

primarily on Housatonic, though a broadly science-based methodology produced data relevant to eachsite component and placed Hunley in a largerhistorical and archaeological context wherebyHunley derived some of its significance fromHousatonic and vice versa. An initial characteriza-tion of USS Housatonic evaluated the wreck’sarchaeological integrity and potential eligibilityfor the National Register of Historic Places.Goals for this part of the survey were to identifythe ship’s key features, extent, and orientationthrough minimum-impact techniques. This wasfollowed by research to interpret the ship’sconstruction, spatial organization, and possiblebattle-damage.

FieldworkAs with Hunley, the entire wreck of Housatonicwas buried under sediment and could only belocated through an examination of the wreck’smagnetic signature. Diving conditions were difficult,with zero visibility the norm in excavationareas and less than 30 cm (1 ft), occasionallyextending to 60 cm (2 ft), outside them. Theseconditions hampered productivity and madephotographic documentation impossible. In additionto low visibility, strong currents occasionallyforced suspension of diving operations. Weatherduring both the 1996 and 1999 seasons was unsettled,and sea states made diving impractical on severaloccasions. Safety lines were used at all timesto guide archaeologists from project boats tothe bottom and from one area of the site toanother.

Adhering to the minimum-impact investigationstrategy of the Hunley assessment, only small,precisely-located test-excavations were conductedon Housatonic. Researchers selected initial test-excavation locations through interpretation ofremote-sensing data derived from the 1996 wide-area survey. These were refined with a jet-probeused to delineate wreck areas not deeply buriedby estuarine sediments. The probe, constructedspecifically for this fieldwork, consisted of a 2.4 m(8 ft) section of 4 cm (11/2 in) galvanized steelpipe connected to a 5 cm (21/2 in) fire-hose with aT-fitting coupled to a water-pump in a boatabove. By opening and closing a ball-valve on topof the pipe, archaeologists could regulate thepressure of water flowing out of the bottom andtop of the steel pipe. The pipe was marked withridges of tape at 30 cm (1 ft) intervals, whichallowed quick determination of pipe depth in thesediment, even in zero visibility. Archaeologists



probed into the sea-bed to characterizearchaeological elements buried beneath themodern bottom. When the probe hit something,listening to the sound the pipe made gave theoperator an idea of the composition of thematerial struck—metal made the pipe ring, woodproduced a dull ‘thunk’, and coal produced acharacteristic scratching sound. In the zerovisibility, 50 m (165 ft) transects of polypropyleneline laid out in cardinal directions over the siteand knotted at 1 m (3 ft) intervals providedspatial control. Through-water communicationsallowed a surface tender to record immediatelyspatial data and observations from thearchaeologist working on the sea-bed. In the caseof the Housatonic site, probing proved invaluablebecause the site produced magnetic gradients ofup to 1000 gammas over a distance of less than7 m (20 ft). These steep gradients made effectiveuse of the hand-held, in-water magnetometerimpossible in some areas. In lower gradient areas,investigators used the hand-held magnetometerto position test excavations over ferrous targets.

Once a test-excavation area was located, anarchaeologist used a standard induction dredgeto remove overlying sediment until features weredistinguishable, or, if nothing was located, until itbecame clear that continued excavation wouldprove unproductive. As data clarifying the wreck’sorientation accumulated, excavation activitiesturned to the stern area to investigate evidenceof the attack and post-depositional processessuch as salvage and obstruction clearing. Primaryfeatures of interest were the boilers and engine,the starboard stern quarter, and the propellerand propeller-shaft assembly. Historical accountsreport that the Hunley attack damaged both thestarboard stern quarter and the propeller area.Once the layout of the wreck was determinedand post-depositional processes understood, theultimate research goal was to document theeffects of the attack. Altogether 321 individualprobe holes in 17 different directions, spanningmore than 300 m (1000 ft), covering an area ofmore than 3,200 m2 (35,000 ft2), were completedover and around the Housatonic. Of these, 43 werecoal, 23 wood, 108 metal and 147 had no contact.The shallowest probe return was 1 m (3 ft) belowthe sea-bed, and the maximum depth was2.4 m (8 ft). Materials buried deeper than 2.6 m(81/2 ft) below the seafloor were not detectable bythe probe.

Researchers excavated three test-trenches inan area of relatively-shallow sediments to recover

some diagnostic artefacts and to refine sitedelineation. One, Trench 2, was immediatelyabove two water tanks which were identifiable onplans of a sister-ship, an Ossipee-class sloop-of-war like Housatonic (Fig. 4). By scaling and geo-rectifying the ship’s plans in the GIS databasebased on the location and orientation of thewater tanks, team members were able to generatereal-world coordinates for other areas of thewreck and to ascertain where the probe lineswould fall when overlaid on an intact Housatonicdeck-plan (Fig. 5). Overlaying probe-lines in thisway also indicated where other extant shipstructure should be encountered with the probehad Housatonic been undamaged and unaffectedby post-depositional formation processes. Asdata developed, it became clear to the team that,although the probe encountered structure wherethe plan overlay indicated it should be, the areaof the starboard stern quarter had producedno contacts at all. This meant that the wreckwas either below the maximum 2.4 m (8 ft)probe depth or that the area of the wreck wasnot present under those probe-lines. Ourinterpretation is that negative contact with thejet probe in the starboard stern quarter area isthe result of that portion being absent and notbeing below the maximum probe depth. Thiscorroborates historical testimony concerningthe nature of the attack and damage sustained,recorded at the Court of Inquiry followingHousatonic’s loss (Bak, 1999: App. A).

Probing and excavation of the Housatonicwreck indicates superior preservation of evenrelatively-small organic artefacts and intactstructural fragments in some areas. Assuming themagnetic contours are congruent with site extent,the Housatonic wreck encompasses more than11,891 m2 (128,000 ft2) based upon the 2 gammaisoline. The area of contiguous probe contacts onthe wreck is approximately 678 m2 (7300 ft2) or5.7% of the total area of the magnetic anomalycaused by Housatonic. The hull-plans for anOssipee-class sloop-of-war show the originalarea, before the attack and post-depositionalscattering, as approximately 550 m2 (6000 ft2) orabout 4.6% of the area of the 2-gamma anomalycontour. Total excavation area for the Housatonicassessment was approximately 31 m2 (336 ft2)which amounts to 0.02% of the total areasurveyed during 1996; 0.26% of the area ofHousatonic’s 2-gamma magnetic anomaly; 4.6%of the total area of contiguous probe contacts; or5.6% of the original hull area before the attack



and post-depositional scattering. In summary,a systematic, but extremely minimal-impactexamination of a large and difficult site producedartefacts in a superior state of preservation,critical data pertaining to wreck orientation anddegree of preservation, and information directlypertinent to understanding the Hunley attack andthe damage it inflicted.

Third AnomalyThis sits approximately 130 m (430 ft) east of theHousatonic wreck. Archaeologists documentedthe object producing the magnetic anomaly ina preliminary manner largely by feel in nearlyzero visibility conditions, and uncovered onlya portion of it. Although only a few observa-tions could be made, they were sufficient foridentification. The object producing the 160-gamma magnetic anomaly is large, roughlybullet-shaped, hollow and made of ferrous metal.It is flat at one end and tapering to a blunt pointat the other. Diameter is 2.6 m (8 ft 7 in) at itslargest end and unknown at the smaller end,

which was not excavated. It is approximately 2.1 m(7 ft) long and lying on its side, largely buriedin sediment. The object was found with a sectionof the round side and part of the large-diameterflat end protruding approximately 22 cm (9 in)above the sea-bed. The visible part of the flat endhas a large oval hole which follows the curve ofthe exposed upper side. Where the flat end joinsthe curving side is a rolled lip approximately 12 mm(1/2 in) high and 25 mm (1 in) wide. Attachedto the side of the object is an approximately20 cm (8 in), semi-circular piece of round iron bar-stock 38 mm (11/2 in) in diameter, with at leasttwo links of open-link chain 22 cm (9 in) longattached to it. The chain disappears into thesediment and was not excavated to its full extent,though an examination of the magnetic contoursderived from the 1996 survey indicated additionalferrous material present.

The Third Anomaly is almost certainly a buoyand probably marked the wreck of Housatonic asa hazard to navigation soon after its loss. The1870 Coast Survey chart of Charleston Harbour

Figure 4. USS Housatonic’s water tanks, located in Trench 2. These tanks provided the wreck’s orientation and a specific,identifiable location within the ship that could be used to geo-rectify the original plans.



shows a buoy marking the wreck. When thischart is geo-rectified to bring it into accordancewith the 1996 and 1999 survey data, the chartedposition is 131 m (430 ft) from the presentlocation of the Third Anomaly and 278 m(915 ft) from the present location of Housatonic.Historical documents report that salvagersdragged the wreck to the silt-line in 1909 toremove the hull as a navigation hazard, afterwhich there was no reason to keep the buoy inplace. Because the buoy was nearly 40 years oldby this time, it was probably at the end of its use-life and consequently was not recovered butprobably sunk at or near its original position.

Fourth AnomalyThe Fourth Anomaly is located approximately137 m (450 ft) north-east of the Housatonicwreck. It is a 6-gamma anomaly produced bya small Admiralty-type anchor connected to a

length of open-link chain buried 1.5 m (5 ft)under the sea-floor. Although the bearing of theanchor’s shank points toward Housatonic’s wrecksite, it is not known whether this anchor isassociated with that vessel or was lost in someother event.

Site-formation processesBurial sequenceBurial sequence data from Hunley were originallysought in multiple lines of evidence because theywere important to interpreting hull-corrosiondata relevant to hull strength. Evidence collectedin addition to the visual examination of hullencrustation characteristics and biological indicatorsdiscussed above, included historical evidence,sedimentary analysis and additional sediment-bound radioisotopes measurement. Historicalevidence for the burial sequence begins soon after

Figure 5. Probe lines from the 1999 USS Housatonic assessment.



the engagement. Housatonic was investigatedin detail in November 1864. In the nine monthssince sinking, the vessel hull had ‘settled in thesand about 5 feet [1.5 m]’ and salvage diversreported that it was ‘very much worm-eaten’(ORN ser. 1:15: 334). A specific search was con-ducted for the submarine at that time. Investigatorsdragged ‘an area of 500 yards [450 m] aroundthe wreck, finding nothing of the torpedo boat’(Lieutenant Churchill in Official Navy Records,cited in Kloeppel, 1987: 93). By April 1870, sixyears later, divers reported that the ‘woodensheathing inside and the flanking [sic] outsideare eaten by worms down to the copper’(Miscellaneous Wrecks, 1871–1888). In 1872,the Army Corps of Engineers contracted forwork on both wrecks: clearing Housatonicwreckage to 6 m (20 ft) below mean low waterand removal of Hunley. But they were unable tolocate the submarine using grappling-hooks. TheHousatonic’s hull presented a navigation obstacleuntil 1909 when salvagers removed an additional2 m (6 ft) of hull by dragging, blasting andremoving the ship’s boilers (Kloeppel, 1987: 93).

The 1996 Hunley assessment demonstrated thearchaeological relevance of sediment analysisand sequencing for determining site-formationprocesses for the area. Researchers collectedadditional vibracore samples surrounding Hunleyand Housatonic during the 1999 fieldwork toaugment earlier samples and to answeradditional questions not addressed in 1996.Cores from the vicinity of Hunley allowed forshear-strength analysis of the sediments (datavital for developing a safe and successful re-covery methodology), while coring in the vicinityof Housatonic allowed additional dating ofdepositional sequences for sediment overlying thetwo principal site components. 210Pb isotopicdating of upper-level sediments in two of thenine vibracores provides age data for sedimentarylayers in the site within approximately the last100 years. Sediment ages for the layers differbetween the two cores, with the core taken closestto Hunley showing older dates shallower, and thecore taken closest to Housatonic having olderdates deeper. These data indicate an overallhigher sedimentation rate near Housatonic (8.9+/− 3 mm/year) and a lower sedimentation ratenear Hunley (7.4 +/− 2.5 mm/year). Net sedimentaccretion on the wrecks was approximately1.2 m (4 ft) over Housatonic and 1 m (3 ft) overHunley. The generally exponential decay of 210Pbas a function of depth below modern bottom

in the vibracores indicates that accretion ofsediments over both Hunley and Housatonic wasnot punctuated by episodes of erosion. This helpsexplain the superior preservation of Hunley aswell as the numerous small and delicate artefactsrecovered during fieldwork on Housatonic.Sedimentary deposition, though not interruptedby periods of erosion, was probably episodic withrelatively large amounts of sediment depositedon site in short periods due to events such asstorms and, as discussed below, changes to coastalsedimentation dynamics caused by human actions.

In addition to direct analysis of sedimentarystratigraphy with vibracores, high-resolutionremote sensing with two different sub-bottomprofiling instruments was accomplished. AnApplied Acoustic AA200 sub-bottom profilersystem produced deep strata seismic reflectivitydata and an EdgeTech Geo-Star FSSB and SB-424 towfish produced CHIRP high-resolution,shallow sub-bottom profiler data. The AppliedAcoustic sub-bottom and CHIRP units arecomplementary in range and resolution andtogether produce a reliable characterization ofunderlying geological structures. The sub-bottomprofiler characterizes deeper strata at a lowerresolution, and the CHIRP depicts shallow strata,which are of primary archaeological interest, inhigher resolution. Combining both instruments’data provides a comprehensive depiction ofseabed stratigraphy that correlates with stratadocumented in the sediments recovered in thevibracores. This correlation of core strata andreflectors allows for very accurate stratigraphicinterpretation from sub-bottom data and facilit-ates reliable projection of core strata analysisover a large area. Geostar CHIRP data revealednumerous paleo-channels buried by marinetransgression throughout the Hunley/Housatonicsite. Of particular interest to an understanding ofsite-formation processes is a distinct reflector inCHIRP images at approximately 1 to 1.3 m (3–4 ft)below the modern bottom.

Geological characterization of the vibracoresproduced evidence of a stiff greenish-greystratum of clayey sediments at a mean depth ofapproximately 1.8 m (5.8 ft) below the modernbottom. Based upon similarities with regionalsediment sequences, this layer is Pleistocene marlfrom the Daniel Island Bed (Weems and Lemon,1993). The result of sediment deposition inestuarine and lagoonal environments duringperiods of lower sea-levels approximately 1.6million to 730,000 years ago, it is characterized as



‘sticky’. The relatively high cohesive strength ofthis Pleistocene layer, particularly in comparisonto the muddy, shelly Holocene sand that lies on topof it, has an important effect on site-formationprocesses for the Hunley/Housatonic site.

An analysis of vibracore stratigraphy,sedimentation rates indicated by 210Pb, historicallydocumented changes in bathymetry and coastalgeomorphology (corrected for sea-level change),an analysis of offshore sediment transportpatterns, and a uniform reflector in CHIRPsub-bottom data at about 1 m (3 ft) below themodern bottom all point to the fact that theHunley/Housatonic site has experienced recentand rapid sediment deposition. The primaryreason for this sediment accumulation is theconstruction of the Charleston Jetties, completedin 1895, which disturbed the dynamic equilibriumof coastal sedimentation and transport andcaused extensive sediment deposition over allelements of the site. Before construction of theCharleston Jetties, the entrance to CharlestonHarbour lay several kilometres south of itspresent location. Under the combined influenceof ebb-tidal flow and north-east-to-south-westlongshore sediment transport, several large sandbars extended more or less due south across themouth of the harbour and impeded maritimecommerce. In February 1857 work began todredge a deep channel directly into the port.With the onset of the Civil War in 1861, however,these efforts halted (Moore, 1981: 18–20).Following cessation of hostilities in 1865, plansbegan again. In 1876, General Gillmore of theUS Army Corps of Engineers finalized acomprehensive plan for harbour improvementincorporating dredging and construction of twolarge stone jetties beginning in 1877 (Moore,1981: 32–33). By 1895, jetty construction wascompleted and deemed a success. Jettyconstruction, however, interrupted prevailingpatterns of longshore sediment transport. Beforeit, waves from the east and north-east intersectingwith the north-east-south-west oriented coastlineresulted in a net southward transport of mobilesediments. The north jetty diverted the south-west-moving sediment further offshore intodeeper water where current speeds rapidlydiminish, and as this happens, increasingly finersediment drops out of suspension. This processhas resulted in a net sediment accumulationoffshore from Sullivan’s Island over the Hunley/Housatonic site (Fig. 6). The bottom sedimentshave accreted at least an additional 1 m since

jetty construction began in 1877, which isconsistent with all other lines of evidencepertaining to burial sequence.

SummaryCumulative sedimentary data derived fromvibracoring operations, including sedimentdating, sedimentation dynamics and geotechnicalcharacteristics, explain site-formation processesfor the wreck of USS Housatonic, and byextension, H. L. Hunley. Muddy, shelly sedimentsstarting at approximately 1.2 m (4 ft) below themodern sea-bed mark the bottom as it was beforejetty construction. This was the approximateposition of the bottom that Housatonic landedon following its sinking on 17 February 1864. By

Figure 6. The effect of 19th-century jetty construction onthe bathymetry outside Charleston Harbour.



26 November 1864, 10 months later, diversreported that Housatonic had settled in anupright position and had scoured into the sandabout 1.7 m (5 ft), forming a bank of mud andsand around it (ORN ser. 1:15: 334). This initialsettling put the keel just into a cohesivePleistocene marl layer. Based on geotechnicalanalysis of cores, the 1864 seabed has an averagecohesive strength of 28.5 bar (414 psi). ThePleistocene layer to which the Housatonic wreckscoured sometime before diver examination 10months after sinking has a cohesive strength of74.1 bar (1075 psi)—an increase of 259%. TheHousatonic’s settling rate decreased dramaticallyonce the hull bottom contacted this firmerlayer. Reduction of the hull cross-sectional areaexposed to the current, caused by the 1873–74salvage activities, probably further decreasedthe scouring and settlement rate. In February1909, additional salvage activity to remove theremaining hull as a navigation hazard, whichincluded dynamiting and dragging the wreckwith chains to the mud-line, presumably haltedany further settling (Fig. 7).

210Pb data analysis from vibracores establisheda consistent chronology for sedimentary accretion

occurring over Housatonic following its sinking.Sediment accumulation was episodic (probablydue to storm activity) but was not interspersedwith erosional periods. Hunley settled andscoured in the same way as Housatonic, thoughin Hunley’s case differences in sedimentationrate due to a location further offshore resultedin overall shallower settling and burial. As withHousatonic, on the night of its sinking, Hunleysettled onto the rather loose, unconsolidatedlayer of sand that overlay the marl layer. Judgingfrom the rate of scour and settling forHousatonic, Hunley settled rapidly through theapproximately 60-cm (2-ft) thick sand layer untilit encountered the firmer layer below. Supportedby the more resistant layer, the scouring andsettling eventually slowed and stopped (Fig. 8).Following scouring to the Pleistocene layer,the upper portions of the submarine remainedexposed and served as a substrate for coralcolonization, as discussed above. After a periodof exposure, longshore sediments diverted by theCharleston Jetties buried the exposed upperportions of Hunley. Ultimately, approximately1 m (3 ft) of diverted sediments buried thepreviously exposed upper surfaces of the

Figure 7. USS Housatonic site stratigraphy.



submarine, and the entire wreck remained buriedwithout subsequent exposure until its rediscoveryin 1995.

Aggregate sedimentation rates indicated by210Pb analysis of 8.9 +/− 2.8 mm/year (0.35 +/−0.11 in/year) on the Housatonic site and 7.4 +/−2.5 mm/year (0.29 +/− 0.10 in/year) on theHunley site account for the different burialdepths observed for each site. This 27%difference in sedimentation rate probably reflectsHousatonic’s location approximately 300 m (1000 ft)closer to shore than Hunley. The near-shorelocation predictably receives more sedimentload from diverted longshore currents. WhileHousatonic is buried an observed minimum of1.3 m (4 ft) below the mud-line, Hunley is buriedabout 1 m (3 ft) deep—a difference of 25%, whichalmost exactly matches the estimated burial ratesfor the two sites.

While Housatonic’s superstructure rotted, wassalvaged, and then dragged to the mud-line,Hunley was not discovered and may not havebeen directly affected by human actions followingsinking. Sediment accumulation completed theburial processes initiated by scouring, andexplains the burial depths of both wrecksobserved in 1995, 1996 and 1999. Multiple lines

of scientific evidence point to rapid burialfollowing sinking, which accounts for the highlevel of preservation of Engagement Sitecomponents. The Third Anomaly is the solefeature not completely covered by sediments.The buoy scoured through the relatively softHolocene sands to the firmer Pleistocene layerbelow and was partially buried by displaced long-shore sediment, but a portion remained exposedabove the present mud-line because of its largediameter (2.6 m or 8 ft 7 in). Sedimentaccumulation is continuing, however, and it islikely that sediments will eventually bury thisfinal component of the Engagement Site.

DiscussionThe Hunley/Housatonic site consists of fourprincipal components: the wreck of the Unionblockade ship USS Housatonic; the wreck of theConfederate submarine H. L. Hunley; the ironbuoy that probably marked Housatonic’s wreck asa navigational hazard from at least 1870 to 1909;and a small, Admiralty-style anchor that mayor may not be related to either Hunley orHousatonic. Historical accounts from the Courtof Inquiry convened to investigate Housatonic’s

Figure 8. H. L. Hunley site stratigraphy.



loss paint a detailed picture of a well-plannedand -directed attack that placed Hunley’s blackpowder ‘torpedo’ at the precise location thatwould deliver a killing blow. By the timeHousatonic’s lookouts saw the approachingsubmarine it was already too late—Hunley hadclosed to the point where the Union ship’s largerguns could not be trained on the submarine. Theclose range at which the submarine becamevisible to Housatonic’s crew provided insufficienttime to slip anchor and manoeuvre out of thepath of the attacking Hunley. Barring failureof the torpedo, the attack’s success was alreadyassured by the time the sailors on Housatonicbecame aware that something was wrong.

Fundamentally, the skill and precision ofHunley’s attack on Housatonic mirrored thesophistication of Hunley as a weapon and asa piece of technology. As Hunley attacked,both Master’s Mate Lewis A. Corinthwait andLieutenant F. J. Higgson from Housatonicreported that the submarine changed course andsteered parallel and towards the Housatonic’sstern before moving in for the final run into thestarboard stern quarter (Bak, 1999: 161–2).Testimony by both Acting Master John Crosbyand John Saunders at the Housatonic Court ofInquiry states that Hunley slammed home thetorpedo in the area of the mizzenmast (Bak,1999: 154). The mizzenmast was a convenientaiming point for the attack—easy to see fromthe small, water-level view port on Hunley’sforward hatch. Assuming the Ossipee-class plansare representative of Housatonic’s interiorarrangement, aiming at the mizzenmast wouldplace the torpedo directly between the powdermagazine, which could be loaded with up to 3969 kg(8750 lbs) of black powder, and an unspecifiedamount of guncotton in the guncotton room(Fig. 9). Secondary explosions in either theguncotton room, the powder magazine, or bothcould result in sympathetic detonations in theport powder magazine, potentially containing anadditional 3289 kg (7250 lbs) of black powder,multiplying the effect of Hunley’s torpedo chargemore than a hundredfold.

Observers aboard Housatonic reported thatthere was no water-plume from Hunley’s torpedoexplosion—evidence that the ship’s hull andthe water-depth dampened the explosion. Theexplosive force did not dissipate upward, butinstead was directed into Housatonic’s interior,indicating a precise charge placement well belowthe waterline where it would have maximum

effect. On 20 February 1864, just three daysafter the attack, Union observers of the wreckreported that the after part of Housatonic’s spardeck appeared to have been entirely blownoff (ORN ser. 1:15: 331). Ten months later, on27 November, salvage divers reported that allbulkheads aft of the mainmast were completelydemolished—further evidence of the explosion’seffectiveness and the manner in which itpropagated through the ship (ORN ser. 1:15:334). In addition to the tamping effect of waterover Hunley’s explosive charge, by attackingtowards the stern of Housatonic, Hunley’s crewwas able to take advantage of the relatively sharpturn of the stern deadrise, which would channelany upward explosive force into the hull. Thesharp deadrise would also have the net effect ofcreating a blind spot where Hunley could place itscharge in relative safety shielded from the Unioncrew’s small-arms fire.

Data relative to torpedo delivery and theprecise charge placement were indirectly notedduring Hunley’s 1996 investigation. Only theupper surface of Hunley’s bow was uncovered,but researchers did not find any indication of atop-mounted spar for torpedo delivery. Althoughall historical documentation indicated Hunleywas equipped with a spar mounted on the uppersurface of its bow, the lack of any indication of aspar or attachment features led archaeologistsat the time to speculate that Hunley probably hada bottom-mounted spar (Murphy et al., 1998c:104–05). This speculation was supported bymagnetic data which indicated a ferrous massextending north-west of Hunley’s hull (thishypothesis was later proved correct duringHunley’s recovery operations in 2000). Inaddition, at the time of Hunley’s attack onHousatonic, Confederates had considerableexperience with spar torpedos, including thenear-sinking of USS New Ironsides by CSS Davidin 1863. Although New Ironsides was damagedduring that attack, it was not sunk, probablybecause the torpedo was not delivered far enoughbelow the waterline. Since Hunley was to be usedonly on the surface, undoubtedly Hunley’s crewwould have considered David’s failure as theyprepared to attack the Union blockade andmoved the spar torpedo location to the bottomof the submarine to deliver the torpedo as farbeneath the waterline as possible.

The physical layout of the Hunley/Housatonicsite’s material remains can provide insighton how the attack unfolded. Before Hunley’s

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Figure 9. The probable area of impact to USS Housatonic from H. L. Hunley’s torpedo.



recovery in 2000, Hunley’s and Housatonic’sremains lay about 300 m (1000 ft) apart on thesea-floor outside Charleston Harbour, Hunleynearly due east of Housatonic. Hunley’s bowfaced 297° magnetic (Murphy et al., 1998b: 76),while the projected orientation of Housatonic’sremains is 316° magnetic (Conlin, 2005: 185)—both are oriented roughly north-north-west, ordirectly into the ebb tide that was flowing out ofthe Charleston Harbour mouth at the time of theattack. Housatonic was at anchor when the attackoccurred, with its bow into the ebbing tide, andit came to rest on the bottom in nearly the sameorientation (Fig. 10). Historical records indicatethat Hunley was on the surface for at least 50minutes after the attack—witnesses both onshore and aboard Housatonic reported seeing ablue light (Hunley’s signal for a successfulmission) about 50 minutes after Housatonic’ssinking. With an ebb tide flowing, it is likely thatafter Hunley backed away from Housatonic anddetonated the torpedo, the crew would have hadto expend significant effort to maintain a positionnear Housatonic, or they may have anchoredthemselves in place. In either case, after at least50 minutes or more, Hunley succumbed to whateverforces eventually caused it to sink. The answer towhat ultimately sank Hunley will have to awaitfurther investigation by archaeologists andconservators during their current research andanalysis of the world’s first successful submarine.

Careful archaeological documentation andanalysis of physical processes on the Hunley/Housatonic site has allowed us to reconstruct thesequence of events during and after the attack,and isolate and identify damage to Housatonic’sremains that can be associated with Hunley’sattack rather than the significant salvage and

obstacle-clearing activities on the site. This isanalogous to what Scott et al. refer to as ‘grosspatterning’, or the ‘composite of battle eventsexclusive of or poorly understood in time’ (1989:146–7). Based on the gross patterning and thehistorical record, we can recognize specific battle-preparations and tactics employed by Hunley’screw, and offer reasonable speculation aboutevents after the attack.

ConclusionExplicitly-delineated research designs led toa methodology for fieldwork that producedobservations concerning Hunley, Housatonic, theThird Anomaly and the Fourth Anomaly withminimum impact to the site. These data wereaugmented with historical research and anunderstanding of the environmental context ofthe Hunley/Housatonic Naval Engagement Siteto set the stage for a broadly-based analysis ofHunley’s attack on USS Housatonic and eventsoccurring to the different site componentsafter the battle. Archaeological data derivedfrom probe-lines and test-excavations supporthistorical accounts of a massive explosioncaused by Hunley’s torpedo, which destroyedHousatonic’s starboard stern. Despite multipleepisodes of salvage and obstacle-removal, thewreck of Housatonic displays a high degree ofintegrity and superior preservation of portableartefacts illustrative of daily life on the Unionblockade. Following its sinking, Housatonic scouredand settled rapidly down through relativelyloose, sandy sediments and then stopped at thefirmer layer of Pleistocene marl. Followingconstruction of the Charleston Jetties, redirectedsediments began burying the wreck, and in1909, salvagers levelled the wreck to the silt line.The Third Anomaly, most likely the buoy thatmarked the Housatonic wreck as a navigationhazard, also scoured and settled to the Pleistocenemarl layer and then experienced partial burial.The Fourth anomaly, a small anchor not con-clusively linked to any of the other EngagementSite components was also buried by divertedsediment flow.

Hunley apparently survived the attack for atleast 50 minutes—long enough to shine the bluesignal light for success to waiting Confederatesentries at Breach Inlet. Hunley’s location, asdiscovered in 1995, matches a reported sightingof the blue light quite well, and may indicate thatsignalling success was one of the last things the

Figure 10. The relationship between the Hunley andHousatonic wreck-sites.



crew of the submarine did. Following sinking,Hunley experienced the same dynamics of scour,settling and burial that covered and preserved theother components of the engagement site. Ananalysis of testimony delivered at the Court ofInquiry convened following the destruction of theUnion blockader, combined with an examinationof the internal arrangement of the ship, paints apicture of a skilful and precisely-executed attackthat delivered a single, killing blow.

As a naval battlefield, the two principalcomponents of the site, Hunley and Housatonic,

derive a large measure of their importancefrom their relationship to each other. The tacticalmode of Hunley’s attack—specifically the natureand placement of the torpedo—left physicaltraces that were discernable even after 131 years,multiple episodes of salvage, and complete burial.As an event of world history, this first-everengagement between a submarine and a surfaceship deserves evaluation in the broadest possiblehistorical, archaeological and humanistic context.Treating the linked shipwrecks as a naval battlefieldis the beginning of that process.

AcknowledgementsThe 1996 Hunley assessment was directed by Daniel J. Lenihan (NPS) and Christopher F. Amer (SCIAA); Larry E. Murphy(NPS) was field director. The 1999 Housatonic assessment was directed by Robert S. Neyland (NHC) and Christopher F. Amer(SCIAA); David L. Conlin (NPS) was field director. Research on Hunley and Housatonic has been generously supported bythe Department of Defense Legacy Resource Management Fund and Friends of the Hunley. Research drew on many organ-izations and both authors apologize to those left out here. For updates on the remarkable work that is ongoing on Hunley goto www.hunley.org. All errors of fact or reasoning are the sole responsibility of the authors.

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