The Search for Graves

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GEOPHYSICS. VOL. 56. NO. 9 (SEPTEMBER 1991): P. 1310~1319. IO FIGS

The search for graves

Bruce W. Bevan*

ABSTRACT strata are so complex that graves cann ot be distin-Over the decades, grave markers in old cemeteries guished. A conduc tivity survey can be degraded by

have been lost. Geoph ysical exploration can some- metallic trash and other small objects in the topsoil: ittimes locate the unmarked burials. The two techniques can give the best results where the earth is distinctlywhich may be best for this search are a ground-penetrat- stratified.ing radar surve y and a soil conductivity survey. Results from n ine surveys are illustrated here. The

A ground-pen etrating radar survey, w ith its capabil- sites are all in the U.S.A. and the graves are not olderity for estimating the depth and shape of buried than the 17th century. Magne tic and resistivity sur-objects, is particularly suitable. With an electromag- veys may be suitable for some sites, but they have notnetic induction survey, the disturbed soil in the grave been very successful for the sites discussed here.shaft can sometimes be detected as a change in elec- The success of these surveys has ranged widely.trical conductivity. Both of these surveys also can from excellent to poor. W hile little archaeologicallocate large metal objects. excavation has followed these surveys, geop hysical

These su rveys have limitations. At some sites, the tests at mark ed grav es show the capability of theradar cannot profile deeply enough ; at others, the soil instruments.

INTRODUCTION* . . . .

the excavated earth is replaced. some topsoil may return to. . . the bottom of the hole and subsoil may end up on top andbrave marke rs nave become lost, destroyed, or misplaced

for several reasons. Wood quickly rots. Stone may break orcrumb le. Vandalism and falling trees also can contribute tothe loss. Some graves may never have been marked.

As time and land development progress, it can becomeimportant to find these old, unmarked graves. Sometimesthey are accidentally encountered during construction andsomeone wishes to determine the extent of the cemetery sotliat it can be preserved. In other cases, it might be necessaryto locate individu al burials so that they can be removed toanother location.The study of old graves also can provide valuable infor-mation about changes in social customs (Brown, 1971;Tainter, 1978; Bartel, 19 82).

THE CHARACTERISTICS OF A GRAVEThe m ost distinctive feature of a grave m ay be the

disturbed soil in the filled excavation. Throu gh the l-2-mdepth of a grave shaft, the soil may change ma rkedly. When

may be spread on the surface. The topsoil can be higher inmagne tic susceptibility than the subsoil. Also, the electricalconductivity of the natura l earth may increase or decreasewith depth. The soil filling the grave shaft could have adifferent electrical an d magn etic stratification than the natu-ral earth. These soil changes could last indefinitely.

Except for recent criminal burials (Davenp ort et al.. 19 88;Davenport et al., 1990) nothing may remain except forbones. While the bones may last for thousands of years insome types of soil, they will ge nerally not be directlydetectable. However, the decay of the body can possiblyalter the chemical composition of the surrounding soil.

The soil also could be less compa cted at the bottom of thegrave sh aft. If a coffin is still partially intact, there could bean air-filled void. Co ffin nails would usually be undetectable,but some coffin fittings could be large metal objects (Bell.199 0). Metallic or lead coffins could be present. If there is aburial vault of brick or stone, there could be an air cavity,and the brick or stone could be moderately magne tic.

Presented at the 59th Annual International Meeting, Society of Exploration Geophysicists. Manuscript received by the Editor March 21, 1990:revised manuscript received F ebruary 5, 1991.Yieosight, P.O. Box 135, Pitman , NJ 08071.6 1991 Society of Exploration Geophysicists. All rights reserved.

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The Search for Graves 1311The soil in the grave shaft might have settled. leaving a Soils in formerly glaciated a reas, such as New England.at the surface. The surroun ding soil can be very complex and can mask buried features on radar

profiles. Stony so il resulting from shallow be drock c an causebe detectable. Metallic debris could have the same problem. Grave digging might have left heaps ofin the depression. The grave marker might have subsoil scattered on the surface. If the velocity of the radard be buried at a shallow depth. Possibly the grave pulse is marked ly different in these soil lenses. the radarwith a pipe or a stone border. which is now images of deeper features can be sheared into complexpatterns. making them impossible to recognize.

While burial practices change with time and location,coffin at a depth of l-2 m. A cemetery could mo re

be on a hilltop than in a valley. It might be possible toof a cemetery even though individual graves

be detectable. Possibly the cemetery was neveralthough the surrounding lan d was: the cemetery

ary could mark a contrast in the stratification orretention of the soil. Trees might have been al-grow in the cemetery, while the surrounding land

if their roo ts have not decayed or if soil scars from

Electromagnetic induction meters

Many of the characteristics described above can be detectedr, the setting is sometimes difficult: If

Electromag netic induction meters can provide a fast mea-suremen t of the electrical conductivity of the earth (Frohlichand Lancaster. 198 6). These instruments, with intercoilspacings of l-4 m, can provide enough lateral and amplituderesolution to detect the contrasting earth tha t fills a graveshaft. They also can act as metal d etectors; this can be goodor bad, depending o n whether the metal is sought or presentas incidental trash. These instrum ents also can measuremagn etic susceptibility. allowing the detection of brick. firedearth, and changes in the thickness of topsoil. Condu ctivitysurveys can be affected by electromagnetic interference inareas with high soil resistivity, such as sand. but they c an bedone over a dry. hard surface such as an asphalt parking lot.

INSTRUMENTS FOR THE SEARCHResistivity meters

Ground-penetrating radar (Vaughan, 1986; Imai et al., 1 987)approxim ate soil profiles, with reflections caus ed by

dielectric co nstant and electrical resistivity. In

lanar stratification, then the chaotic soil which fills the

ects (B-E) also can be present.

Resistivity su rveys, with four earth-contacting electrodes.can provide informa tion similar to that from EM conductiv-ity surveys. Th e Wenner configuration has low lateral reso-lution, but spatial oscillations in the measurements that havea high frequency could define the area of disturbed earth ina cemetery (Carr. 1982 ). Other electrode configurations.such as the pole-pole or dipole-dipole arrays. would gen er-ally be more suitable for the mapping of individual graves.Resistivity pseudosections also could provide evidence ofgrave shafts (Ellwood. 199 0).

MagnetometersRada r is also excellent for finding air-filled voids and metalIf brick vaults are suspected, a magn etic surve y sh ould be

considered, for brick is rather m agnetic. While the nails in awooden coffin might cause a magnetic anomaly of less thanI nT. other iron hardware on the coffin might be massiveenough to be detectable. If the backgroun d spatial variabilityof the magnetic field is small, the destratified soil of refilledgrave shafts might be detected (Ralph, 196 9). There isenough iron debris at many cemetery sites for magneticsurveys to be of little value.

A El C D EI I--q@=- -aD wwI I II I I I I I I I II I: L-J

I I I IL-J L-J !___!

1. The hachured areas show soil contrasts that mighta grave on a radar profile. The broken lines indicate

Other instrumentsMan y other techniques hav e also been employed in the

search for graves or tombs: seismic (Linehan, 195 6), SP(Wynn and Sherwood, 1984), microgravity (Lakshmananand Montlucon. 1987; Blizkovsky, 1979). In Europe, aerialphotograph y has been particularly successful in the explora-tion for flattened remnants of ancient burial mounds (Wilson,1975).


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1312 BevanEXAMPLES OF GEOPHYSICAL SURVEYS Touro Cemetery

The first examples will illustrate ground-penetrating radarsurveys; results from conductivity surveys will follow . Th eexamples which are shown here have a gre ater clarity than isfound at the average site. Detailed notes are given in theAppendix; these will allow the possible unmarked graves tobe relocated. The notes also describe the failings of so megeophysical surveys.Carroll House

As part of a geop hysical survey at a historical house inAnnapolis, Maryland, a radar survey examined a cemetery.Figure 2 is a rad ar profile that crosses I4 marked graves;their locations are indicated by g. The sides of the profileshow the estimated depth in meters and the delay time of thereflection. On the left, six of the seven graves are indicatedby small hyperbolic arcs; the seventh grave is only faintlydetected. However, none of the graves on the right sidecause noticeable radar reflections.

The seven graves on the left are from the period 1954-1975. The seven graves on the right are reburials, of bonesonly, from another cemetery; the original burials were fromthe period 1845-1877.Rockville B aptist Church

At many old cemeteries there are som e marked graves,but it is suspected hat there could be additional graves thathave lost their markers. This is a good setting for a geophys-ical survey, for tests at the marked graves can su ggest hereliability of the geophy sical survey.

An example of this is provided by a ground-penetratingradar survey of a 19th century cemetery where there wasonce a Baptist Church in Rockville, Maryland. There areabout 33 graves that are m arked with stones at this site, butit w as thought that there also m ight be additional graves. InFigure 3, the radar profile crosses four m arked graves. Atleast two of these appear to have been detected by the radaras reflections at a depth of 1-2 m. On the left side of theprofile, there are three additional reflections that are similarto those from the marke d graves. These could be unmarkedgraves.

As the soil strata become more complex, graves canbecom e indistinguishable in the clutter on th e rada r profiles.The soils found in glacial and periglacial terrain can cau severy com plex radar profiles.

In New port, Rhod e Island, there is a cemetery that datesback to the 17th or early 18th century. Figure 4 illustrates thecomplexity of the radar profiles from the site. Stones indi-cate that graves are at the two locations marked g. While the

FIG. 3. Rockville B aptist Church. Four graves that aremarked with stonesare indicated by the letter g; the radarreflections from four possible unmarked graves are indicatedby & p. The vertical sca les sho w the round-trip delay tim eof the reflection and also the estimated range to the reflector.

FIG. 2. Carroll House. Fourteen marke d graves are along theline of this radar profile; only six of them w ere detected bythe radar. FIG. 4. Touro cem etery. A m arked grave at g has areflection at a depth of I m.


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The Search for Graves 1313marked grave on th e left h as a clear reflection, the m arked south profile with a strong, isolated reflection. Th e profile ofgrave on the right causes no distinctive reflection. Note that Figure 5b w as made in an east-west direction and sho ws thatthe horizontal scale of the rad ar profile is compressedby a the object is longer in that direction; it is about l-2 m long.factor of about five relative to the depth scale. This reflection is possibly caused by an unmarked grave.In Figure 4, the re are two add itional reflections that couldreveal unmarked graves; these are at a de pth of about I mand are indicated p.Bruton Parish Church

The depth of a radar reflection is the primary clue that thereflection might be from a grave; a secondary clue is pro-vided by the shap e of the reflection. While the size informa-tion from radar is rather crude, it can sometimes reveal thata buried object is distinctly longer in one direction than theother; this can indicate a grave.An example of this was found at an 18th century church inthe middle of Williamsburg, Virginia. Figure 5a is a north-

The radar profiles also reveal several technical points. Inthese and the other profiles here, b oth positive and negativesignals are printed identically as black bands . The reflectionat a depth of I m in Figure 5a is so strong that at least fivehalf-cycles of the reflection are distinct. Furthermore, thereappears o be a second reflection, a reverberation, a t a depthof 2 m; because of the weake r signal, only three half-cyclesof that reflection are apparent. The long arms on the hyper-bolic reflection suggest hat the reflectivity of the object islarge over wide angles; a reflection is detected at least 2 mdistant from the middle of the object. The profile of Figure 5bis about I m north of the middle of the object; this causes h e

(a ) (b )

(4

FIG. 5. Bruton Parish Church. (a) This is a north-south radar profile over a possible grave. (b) An east-west profileshow s that the object is wider in that direction. (c) Buried metal decreases he apparent conductivity; the contourinterval is I mS/m. The broken lines locate the lines of the two radar profiles. (d) There is also buried iron o r brick;the contour interval of this magnetic map is IO nT.


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1314 Bevanreflection there to be detected at a slightly greater range,which is greater than the actual depth of the object.

A conductivity survey was done over the possible gravewith a Geonics EM31 electromagnetic induction m eter.Figure 5c sho ws a pattern typically cause d by bu ried metal:low values over the object with slightly higher values aroundit. Th e low values are simply caused by the inherent nonlin-earity of the instrument near excellent conductors. A resis-tivity pseudo section was m ade across this object, but itrevealed no anomaly.

A magnetic survey was also done; Figure 5d show sa 40 nTmagnetic high with evidence of a magnetic low on the north.This could be caused by roughly 3 kg of iron at a dep th ofabout I m. A larger mass of brick also could cause theanomaly.

All the evidence suggests hat there is an unmarked graveat a depth of I m; it could contain a metal or metal-framedcoffin, and it is also likely that iron or brick is in the grave.The Poor Farm cemetery

A pau pers cem etery in Rockville, Maryland, has gravesdating back as early as 1789. None of the graves is marked.A radar survey was done at this cemetery and Figure 6shows one profile with a reflection that was thought likely tobe caused by a grave. This profile w as made along a line ina north-south direction; perpendicular profiles, directedeast-west, show ed that the reflecting object was longer inthat direction. Ho wever, excavation at this location showe dthat the cause of the reflection was a natural change in thecomplex soil strata that are found at this site.Mount Vernon

A historical record has suggested hat the graves of slavesare located on a ridge close to G eorge Washington s tomb. InFigure 7a, this tomb is marked with a rectangle in the upperright corner; the contour lines, with an interval of 5 ft (I .5m), show the wood ed ridge to the southwest. While there isa commemorative monument on the ridge, no graves aremarked. A radar survey may have located about 50 un-marked graves; these are show n by small ovals in Figure 7a.

Figure 7b shows reflections that could be cau sed bygraves. By making closely spa ced profiles along perpendic-ular paths, it was found that most of the reflections weredistinctly broad er in the east-w est direction than they we renorth-south. This, combined with the depth of the reflec-tions, sugg ests hat these reflections may indicate unm arkedgraves. Since the example above shows that quite naturalchang es in th e soil can c ause radar reflections that areidentical to these , this survey h as indicated only the p ossiblelocations of graves.Ely, Minnesota FIG. 6. Poor Farm cemetery. The radar reflection in themiddle of this profile looked like it w as caused by a grave,At a cemetery in this town, only one grave is marked with but it wa s not a grave. It was caused by a natural change ina stone. A radar profile wh ich crossed the grave show ed a the soil strata.clear reflection at a depth of about I m. The re are I8 shallowoval depressions n the area, suggesting hat there could be


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64

(b ) 10 mN70 I I

0

20

40ns

P PP P

FIG. 7. Mount V ernon. (a, left) Possible unmaby small ovals on this topograph ic map. (bunmarked graves are evident on this radar pro


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1316 Bevanunmarked graves. Figure 8 shows three possible graves, allunmarked.

The area is wooded and it is possible that som e of thedepressions could be caused by uproo ted trees that havelong since decayed. There are three possible associations:

Grave-like reflections at locations withou t depressions ,grave-like reflections where there are depressions, anddepressions where there are no reflections.

At this site, nine examp les were found in each of these threecategories. It is uncertain w hether the depressions or theradar reflections are more reliable indicators of graves.

Kettering Shaker cemeteryThere is a 1 9th century Shaker cemetery in Kettering,Ohio. Historical evidence suggested ts location and a mon-

ument was placed there. During construction in the area,excavations about 100 m from the m onument exposed buri-als and an archaeological test was begun. The upper layer ofsilty soil was removed to a depth of less than I m but graveshafts could no t be seen in the und erlying gravelly s oil.

A conductivity survey was done with a Geonics EM38electroma gnetic induction meter after initial tests show edthat the exposed coffin remains, which contained metal

FIG. 8. Ely, Minnesota. Three possible unmarked graves aremark ed with the letter p here; the radar reflections are atdepths of l-2 m.

fittings, were detectable at a short distance. B ecause of thenormal nonlinearity of the instrument, metal that is closerthan about I m can cause low or negative readings ofapparent conductivity; at a somew hat greater distance, thereadings can show high conductivity.

About 25-50 anomalies, showing low or negative values ofapparent conductivity, were found in areas where no burialscould be seen. Six of these anomalies were tested by shallowexcavations and five graves were partially exposed at depthsof less than I m.

Figure 9a sho ws the type of conductivity anomalies thatwere found: low or negative readings surrounded by highs.While the two marked areas were not excavated, they areprobably grave s that contain coffins with metal han dles andpossibly metal frames. The burials appear to be slightlyoblique to the measurement lines; this cau ses each anomalyto be split into two areas.Figure 9b is a m agnetic map of the sam e area; there is nosignificant anomaly in the area of the conductivity lows.

Neither geophysics nor excavation could detect anygraves near the cem etery monument.

Lamington Black cemetery

Another example of an EM38 conductivity survey done ata cemetery is shown in Figure 10. Several profiles in thecemetery gave evidence of a correlation between the loca-tions of know n gra ves and conductivity highs. There fore,some of the conductivity highs shown in the figure could becaused by unmarked graves.This site is a cemetery in Lamington, New Jersey. It ispossible that the conductivity highs are caused by soilcontrasts in the grave shafts, rather than by metal.

CONCLUSIONFor the sites that have been investigated, the ground-penetrating radar has had the greatest success at locatingunma rked graves. The best conditions for this instrument are

at sites where the rada r detects few underground objects andeither no apparent stratification or only weak, planar strata.The soil should be high in res istivity, pos sibly greate r than200 R * m. The worst conditions for radar are conductive,clayey soils. Complex profiles, such as can be found in area swith glacial till or rocky soil, can make it difficult to isolateany possible graves. The radar reflections from the depth ofthe burial appea r to provide the strongest evidence for agrave; reflections that a re elongated in one direction relativeto the perpendicular direction also sug gesta grave.Measurements of electrical conductivity also appear to besuitable for the search for graves. L ow values can indicate aproximity to metal, but high conductivity h as been associ-ated with g rave shafts at one cem etery.

These surveys have found no guarantee of success. Geo-physical evidence has suggested that there were graveswhere there were none; known graves have also beeninvisible to these surveys.


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The Search for Graves 1317

(4

2 m P

(b)

FIG. 9. Kettering Shaker cemetery. (a) Apparent electrical conductivity is contoured at an interval of I mS/m. Twograves could be indicated at p in this Shaker cemetery. (b) The magnetic map of the same area. contoured at InT. shows no anomalies at the conductivity lows.

20;

I:

10

:

iIIII\

0

Apparent electrical conductivity,mS/m

3 ft W of center3 ft E of center

0 20 60 80 100N coordinate, ft

120 140 160 180

FIG. IO. Lamington Black cemetery. Three parallel conductivity profiles are spaced by about 0.9 m. There is adepression at y that is likely a grave and high readings were found there: other anomalies marked p could bemore unmarked graves.


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1318 BevanREFERENCES

Bartel. B.. 1982. A historical review of ethnological and archaeo-logical analyses of mortuary practice: J. Anthropol. Archaeology.1, 32-58.

Bell. E.L.. 1990. The historical archaeology of mortuary behavior:Coffin hardware from Uxbridge. Massachusetts: Historical Ar-chaeology. 24, 54-78.Blirkovsky, M.. 1979, Processing and applications in microgravitysurveys: Geophys. Prosp.. 27, 84X-861,

Brown. J.A., Ed.. 1971, Approaches to the social dimension \ ofmortuary practices: Mem oirs Sot. Am. Archaeology. no. 25.Carr. C., 1982, Handbook on soil resistivity surveying: Center forAm. Archeology Press.

Davenport, G.C.. Lind emann. J.W., Griffin. T.J.. and Borouski.J.E., 1988, Crime scene investigation techniques: The LeadingEdge. 7, no. 8. 64-66.Davenport, G.C.. Griffin. T.J.. Lindeman n. J.W.. Heimm er. 0..1990, Geoscientists and law enforcement professional5 worktogether in Colorado : Geotimes. 35, 13-15.Ellwood. B.B.. 1990. Electrical resistivity surveys in two historicalcemeteries in northeast Texas: A method for delineating uniden-tified burial shafts: Historical Archaeology. 24. 91-98.Frohlich. B.. and Lancaster, W.J.. 1986. Electromagnetic wrveying

in current Midd le Eastern archaeology: Application and evalua-tion: Geophysics. 51, 141~1425.

Imai. T.. Sakayama. 7.. and Kanemori. T.. 19X7. Use of ground-probing radar and resistivity survey\ for archaeological investiga-tions: Geophysic\. 52, 137-150.

I.akshmanan. J.. and Montlu con. J.. 19X7. Microgravity probes theGreat Py ramid: The Leading Edge. 6. no. I. l&17.

Linehan. D.. 1956. A seismic problem in St. Peters Basilica.Vatican City. Kom e. Italy. in Lyons. P.L.. E d.. Geophysical casehistories: Sot. E xpl. Geophys.. vol. 2. 615-692.

Ralph. E. K.. 1969. Archaeological prospecting: Expedition. I I. no.2. l-1-21.Tainter. J.A.. lY78. Mortuary practices and the study of prehistoric

social systems. in SchifTer. M. B.. Ed.. Advances in archaeolog-ical method and theory: A cademic Press. vol. I. 105-141.

Vaughan. C.J.. 19x6, Ground-penetrating radar surveys used inarchaeological investigations: Geophysics. 51. 595-604.Wilson. D.K.. Ed.. 1975. Aerial reconnaissance for al-chaeology:The Council for British Archaeology. Research Report no. 12.

Wynn . J.C.. and Sherwood . S.I.. 1984. The self-potential (SP)metho d: An inexpensive reconnaissance and archaeological map-ping tool: J. Field Archaeology. 11, 195-204.

APPENDIXNOTES ON THE SURVEYS

My thanks go to the sponsors and coordinators of thesesurveys: the ir investment in these tests will aid others in thesearch for graves.

For the surveys illustrated here, the ground-penetratingradar was a SIR System-7. from Geophysical Survey Sys-tems. Range scales on the profiles have been estimated by ageome trical analys is of hyperbolic reflections: the verticalscales also show the round-trip delay time of the reflections.For each example, the electric d ipole of the antenna w asperpendicu lar to the line of traverse. The two electroma g-netic induction meters were from Geonics. The E M38 has anintercoil spacing of I m, an operating freque ncy of 13.2 kHz.and a detection range of about I.5 m: the EM31 has anintercoil spacing of 3.66 m. an operating frequency of 9.8kHz, and a detection range of about 6 m.

Figure 2: This line was profiled with a model 31 02 radarantenna (having a spectral peak at about 315 MHz) on 20March 198 7. For this and the other illustrations here. ticmarks on the top of the profile are at 5 ft (I 3 m) intervals.The depth sc ale assume s a pulse velocity of 1 0.7 cmins. T hesoil resistivity is 50-80 f1 . m. The survey was coordinatedby Pau l Shacke l, then with Historic Annapo lis but now withthe National Park Service, and was sponsored by theCharles Carroll of Carrollton 250th Anniversary Committee.This is part of the property of St. Marys Rom an CatholicChurch and is located on Duke of Gloucester Street. Gridnorth was a magnetic bearing of 5 degrees and the southeastcorner of the Carroll House is at coordinates N166 E47;these coordinates, like all the others here, are in feet. Th eprofile in the figure is line N 140. The ground surface is mownlawn.

Figure 3: The survey was done with a model 31 05 (180MHz ) antenna and the pulse velocity is 7.6 cmins. Thesurvey was done on 5 June 19 86 for Peerless RockvilleHistoric Preservation and was coordinated by EileenMcG uckian. The site is located on Jefferson Street and thesurface is mown lawn w ith only a few trees. The are a is

urban and a mode rate am ount of interference was detectedfrom other tran smitters. The upper 1.7 m of the soil has aresistivity of abou t 1 100 0 * m : below that the resistivity isabout 370 0 . m. The reference point for the survey was thesouth end of a grave stone for Elizabeth Braddock (18561870 ). The illustrated profile is line WS. G rid north is amagn etic bearing of 5 degrees and extends parallel to a lineof graves.

Figure 4: The profile w as made with a model 3102 (315MHz) antenna on 23 May 1985. The pulse velocity isassume d to be 8.8 cm/m. The electrical resistivity of theearth was not measured , but the soil is probably sand andgravel. The survey was done for Joan Gallagher at the PublicArchaeology Laborato ry (Pawtu cket, Rhode Island). Infor-mation about the site was provided by Berna rd K uzinitz, thehistorian of the Tou ro S ynagog ue. The grid reference point isthe eastern corner of the bounda ry fence: the grid is alignedwith this fence and grid south is a magnetic bearing of 219degrees. The profile is line W22 .S. The m arked grav e ofJacob Lopez is at S7l. The surface is mown lawn with sometrees and bushes.

Figure 5: The radar antenna was a model 3105 (180 MHz)and the depth scale assumes a pulse velocity of 8.2 cmins.This survey w as done on l-2 April 1985 for John Milewskiand John Pillsbury and was funded by the Veritat Founda-tion. The EM survey was done with the magnetic dipolesvertical an d at an elevation of abou t I m. The ave rages ofpairs of readings are mapped here; one with the bar of theinstrument north-south and the other, east-west. The mea-surement spacing was 5 ft. The magnetic survey was donewith a sensor height of 5 ft (I .S m) and a Scintrex MP-2proton magnetometer. The average magnetic field was 53 960nT; no temporal correction was made to the data and theFredericksb urg A-index was 1 6 on the day of survey. Themeasurement spacing was 2.5 ft (0.76 m) and traverses weremade east-west. The soil resistivity at the site is abou t 400R . m in the upper 0.3 m and 135 n . m below that. The


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The Search for Graves 1319done with the Wenner array

nter-electrode spacings of 2.5, 5, and 7.5 ft (0.76, 1.5.2.3 m). The reference point for the survey was the

corner of the tower of the present church and thealigned with this tower. The s urface is covered by

Figure 6: The radar had a model 31 05 (180 MHz) antennais assum ed to be 7.3 cmins. This

dinated by Doug Comer and Paul Inashimaeology Center. Nation al Park Service) andRobertson (Montgomery Coun ty Attorneys Office)

was sponsored by Montgomery County. The survey wasperiod of 27 April-4 May 1986. The illustration

from line E355 . T he site was cleared of brush and bare soile excavation of the site was directed by Diane

Service Center, Nation al Pa rk Service): thisthat the soil strata had complex, undula ting inter-

at two areas where graves were suggested by the

three areas where none were interpreted from thealso made w ith a magnetometer and a conductivity

ile they revealed no anom aly, a resistivity pseu-nd a 20 percent increase in the resistivity at the

radar reflection. The soil resistivity here wasm in the upper 0.6 m and 2000 R . m below

Figure 7: The radar antenna was a model 310 2 (315 MHz)es a pulse velocity of 7.6 cmins.

survey was done on 7-8 January 1985 and was directedtlaw; Dennis Pogue is the current d irector of the

by the Mou nt Vernon Ladies A ssociation of theFor the radar survey. profiles were spaced by 2.5 ft

sistivity profiles on two lines showed no corre-1 radar reflections.

urements found an average resistivity of 350. m with anomalies of 10 0 0 . m using the Wenner array

ectrode spacing of 5 ft (I .5 m). A magne tic su rveyan iron-containing fence and

not correlate with rad ar reflections. The base map wasy Mou nt Verno n. The reference point for the

ith the north-going path: this is a magn eticdegrees. T he illustrated profile is line W30.

surface is covered by leaves and the average d istancetrees with trun k diame ters greater tha n 5 cm is

I m.of the burials. Th e survey did not explore the

Figure 8: The profile w as made with the model 3 105 (180antenna. The depth scale assumes a pulse velocity of

9. I cmins. The survey was done over the period IS-20 June1984 for Gordon Peters. USDA Forest Service. as part ofcontract 43.63A 9-4-86 4. The average resistivity of the earthis about 2300 II . m: the soil is mostly gravel but containssome boulders 0.3 m in size. The rad ar determined that thedeeper, natura l strata dip down 13 degrees to the northwest.Resistivity profiles across five possible graves with theWenner array and an electrode spacing of 5 ft (1.5 m)detected n o anom alies where there w ere rada r reflections.The average spacing between trees is about 3 m in the areaof survey: their trunk diameters range between 9 cm and 45cm. The su rface is covered by pine needles. The co ordinatesystem was set up by the U.S. Forest Service and alignedwith magnetic north: the Isaac Rova (1866-1898) grave islocated at N 1 2 E30. The site is on the property of the ElyService Center and the area is rural.

Figure 9: This survey was done on 18 August 1985 andsponsored by the Dayton Power and Light C ompany as partof an archaeological survey done by Greenhouse Consult-ants and directed by Joel Grossman. The conductivity mea-surements were made with the Geonics EM38 on the groundand with its dipoles vertical and along an east-west line. Thiscauses the elongation of the anomalies in the east-westdirection. The measurement spacing was I ft (0.3 m) andtraverses were made going east-west. The magnetic su rveywas done with a Scintrex MP-2 proton magnetometer withits sensor at a height of 2.5 ft (75 cm). Measurem ents weremade at intervals of 1 ft (0.3 m) along east-going traverses.The average field is 55 900 nT. Th e temporal variation duringthe survey was 6 nT and it was not corrected. Grid north istrue north and a magnetic bearing of about 0.5 degrees. Theresistivity of the silt here is 120 IZ . m and the sandy gravelwhich is below has a resistivity of about 180 0 0 * m. Fewerthan I percent of the gravel pebbles were strongly magnetic.but they caused the complex magnetic map. Th e 0. 0 pointon the figures has truncated state plane coordinates of N898E603. The metal fittings on the coffins were iron, lead,silver-plated metal, and possibly copper. Som e wood re-mained from the coffins. The one conductivity anom aly thatwas excavated but which was not a grave was apparentlycaused by a lateral contrast in the sand and gravel.

Figure IO: This survey was done on 1 7 October 1986 forJohn Seidel, Pluckem in A rchaeological Project (now at theUniversity of Marylan d), by F. Estrems and Joanne Galinisof Rutgers University. The Geonics E M38 had its dipolesvertical and along an east-west line. The m easurem entspacing was 2 ft (0.6 m). The area is wooded but the brushwas cleared. It appears unlikely tha t the geom etrical effect ofthe depression cause d the conductivity high. With the highconductivity of the soil, the radar was not successful: theradar profiled several dozen known or likely graves but onlyone might have been detected. Magne tic and resistivitysurveys were not helpful either. The illustrated line follows amagn etic bearing of 15 degrees. The con ductivity low at N94is near the grave o f Samuel Lane. The site is on Cowperth-Waite Road in a rural area.

The Search for Graves

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