Swedish Granary/Atlantic White Cedar Project

Cumberland County Historical Society

Greenwich, NJ

Dendrochronology Progress Report

Dr. Edward R. CookWilliam J. Callahan, Jr.

November 2014

Introduction

In August, 2008, while engaged on an independent project studying other sites in the vicinity,dendrochronologists William Callahan and Dr. Edward Cook were asked to assist in the evaluation of astructure identified as being of historical importance. They therefore collected 10 wood core samplesfrom a timber building known as the "Swedish Granary", presently located on the grounds of theGibbon House at 960 Ye Greate Street, Greenwich, NJ 08328.

In 1973 this structure had been identified by G. Edwin Brumbaugh, PAIA, and Albert F.Ruthrauff, AIA as being of early Swedish settlement origin, and they suggested a construction date ofcirca 1650 and speculated that it might have functioned as a grain storehouse. Also proposing an earlySwedish colonial origin for the building were Carl & Alice Lindborg, who referenced the work of Dr.Amandus Johnson, author of “The Swedish Settlements on the Delaware, vols. 1&2” (1911). At thetime a decrepit farm outbuilding standing in Lower Hopewell Township, it was disassembled, moved toand restored at its present site in 1976. It is currently owned and maintained by the Cumberland CountyNJ Historical Society (CCHS).

The logs used in the construction are Atlantic White Cedar (Chamaecyparis thyoides), a speciesindigenous to a narrow coastal region along the Atlantic, growing in fresh water swamps and bogs.Although commonly called "Atlantic White Cedar", it is horticulturally not a cedar but a cypress.However, throughout this report the common name will be employed, often shortened for convenienceto AWC. The wood is lightweight, easily worked and highly resistant to decay, and in southern NewJersey was used for shingles, barrels, siding, boats, and occasionally as primary timber for construction.

The field sampling of the Swedish Granary resulted in ten wood cores of good quality, butlaboratory analysis afterward was unable to provide dates for the materials. To make precisedendrochronological datings it is necessary that the field samples be correlated with an absolutely dated"master chronology" (aka "absolute chronology" or "standard chronology"), which specificallyidentifies each calendar year. This master chronology must be compiled previously, of multiple samplesof the same species sharing the same ecological region. In the case of the Swedish Granary, no suchmaster existed at the time, and therefore no dendrochronological datings were possible.

Although the 2008 sampling did not succeed in providing dates, awareness of the potential ofdendrochronology to contribute irrefutable evidence to the debate about the age of the Swedish Granaryremained. It was realized that the absence of a regional master chronology had precluded successfulanalysis, and that a targeted effort could redress the limitation: if a master chronology for AWC couldbe compiled, then an absolute dating of the timbers used in the construction of the Swedish Granarycould be possible. To that end, in 2013 the Cumberland County Historical Society NJ applied to andwas granted funding from New Jersey Historical Commission to support the creation of an AWCmaster chronology, with the intent to to date the Swedish Granary. Moreover, it was understood that theproject, if successful, would make possible dating of other historical AWC structures in the region.

Theory and Methodology

The word dendrochronology derives from Greek dendron/tree + kronos/a space of time. Thattrees develop annual growth rings in response to ecological conditions, and that these growth rings canbe used to align wood specimens chronologically, is an old concept. In the 3 rd century B.C. the Greekbotanist Theophrastus speculated on the correspondence between ecological factors and tree-ringdevelopment, and Leonardo da Vinci noted in the 15th century that the ring growth patterns of newlyfelled trees reflected weather variations that he remembered from his youth. In 1737 French naturalistsDuhamel and Buffon performed a "crossdating" of tree rings based upon a severely frost damagedgrowth ring caused by an unusually harsh winter in 1709.

But it wasn't until the 1920's that dendrochronology began to be utilized in a formally scientific

manner. An American astronomer, A.E. Douglass, was searching for correspondence between weatherand sunspots, a solar activity that occurs with more or less cyclical regularity. He hoped to trace theeffects of sunspots in tree rings, which he knew constituted an acceptable record of past climatologicalconditions. Although not successful in this experiment, Douglass noted that similar growth patternsappeared in wood samples collected throughout a very wide area in southwestern USA. In many casesthe patterns of even distant samples could be positioned upon each other like a jigsaw puzzle, somepieces longer and some shorter, eventually producing an overlapping collection - a "chronology"- thatstretched much farther in time than any one sample.

In theory dendrochronology is simple. Trees expand around their outer diameter as they grow,and normally each year's expansion becomes visible in the wood as a single ring. Ring development isa complicated response to local growth conditions, including factors such as temperature, precipitation,species, soil type, variations in sun, wind, etc.; in general, good ring growth reflects good conditionsand bad growth bad conditions. By measuring the size of the annual rings, i.e. measuring the change inring width from year to year, a pattern of growth over time can be established. In theory, all of the treesin an ecological region share similar growth conditions and consequently all produce similar annualring patterns, allowing comparison of their measured patterns with each other. In actual practice,measurement series from contemporary samples can vary greatly and even duplicate series from thesame tree are never precisely alike. Comparison can prove extremely difficult or even impossible to do.

Dating a sample requires not only a quality measurement but also the previously executedcompilation of local growth patterns over time, the "master" or "standard" chronology. This compiledmeasurement represents the mean growth rates for the species and region under study, and is created byoverlapping, more correctly crossdating, measurements from a large number of samples. Generally thisprocess is begun using samples from living trees, for obviously their outermost rings are of known date.Specimens are collected from progressively older sources, from buildings or art objects or sub-fossillogs, etc., which are then measured and mathematically overlapped upon the measurements from theliving trees and from each other. As this process continues a chronology longer than any single sampleis constructed, stretching back in time and absolutely dated by the samples taken from the living trees.

To illustrate simply, assume for example that a researcher in 2010 takes samples from a grove of200-year old trees. The measurements of its growth rings thus represent the years 1810-2010. Samplesfrom a nearby structure built in 1910 with 200-year old trees are collected, measured, and added to theones from the living tree samples. With a 100-year overlap between them, (1810-1910) a mathematicalmean is calculated from the two sources and the revised master chronology now covers 1710-2010.Another site is sampled, this one built in 1810 with 200-year old trees, supplying timbers with anoverlap of 100 years on the early portion of the master (1710-1810), and again the measurements arecompiled and a revised mean calculated. Now the master chronology covers 1610-2010. This process isrepeated until there are no samples older than those earliest in the master chronology. In this way somechronologies, for certain species in certain regions, have been produced that exceed 10,000 years inlength.

Douglass was able to compile a very long master chronology for a species of pine found inAmerica's southwest, with each calendar year on the the chronology represented by multiple individualmeasurements compiled into the standardized mean measurement of growth. He hypothesized thatsince each ring in the master represents a single year of growth, any independent pattern that could besuccessfully compared to it could be assigned to a specific year by its last growth ring. Douglass usedhis master chronology to date to the 13th century A.D. samples from various abandoned Indiandwellings in Arizona and New Mexico. After publication of his results, dendrochronology receivedwidespread attention in the scientific community. Standardized in practice and computerized to assistwith processing the mathematics, modern dendrochronology is practiced worldwide, assisting not onlyarcheology and architecture, but art history, climatology, geology, hydrology, vulcanology, et alia.

Modern dendrochronology relies heavily on statistical evaluations to aid in synchronizing

crossdating positions between series, and to determine the strength of correspondence between them.Specialized computer programs evaluate the massive amounts of mathematical data, sometimesinvolving thousands of individual series comprising millions of data points, and establish positions ofcorrespondence exhibiting high degrees of statistical similarity. It is the responsibility of thedendrochronologist to evaluate this information, for in practice random statistical correspondencebetween series may occur at multiple positions, and these "false positives" must be recognized anddisregarded.

The wood samples themselves are collected using a variety of techniques, the particular mannerdictated by the type of object. Most commonly samples are taken using specially designed andmanufactured drill bits, which extract thin cores efficiently and with negligible harm; aestheticconsiderations are satisfied by carefully selecting locations for drilling. Occasionally an artifact can betaken whole for measurement in the laboratory, or if permissible a piece may be sawn and removed.Measurement in place can be done using a loupe after some surface preparation, but this method isextraordinarily time-consuming and inevitably yields imprecise data sets, and so is used very rarely.

In the laboratory the samples are assigned identity numbers and the surfaces carefully preparedto allow accurate measurement. Each sample is examined ocularly on a movable stage that passesunder a microscope, the operator controlling the speed and distance of the movement. As it passesunder, the researcher uses crosshairs in the reticle to measure each growth ring on the perpendicular, toa precision of .01mm, and the width is recorded. A single sample may contain hundreds of rings, somewider than 10mm -a centimeter- and some as small as .02mm - only one or two cells wide. Themeasurements are entered into the computer database, easily managed and accessible.

Swedish Granary AWC ProjectStatus and Results

One inescapable circumstance guided the organization of the AWC Project: without a functionalmaster chronology, no dendrochronological dating of the Swedish Granary could be possible.Therefore, development of a suitable standard chronology for Atlantic White Cedar (Chamaecyparisthyoides) for dating historical structures in southern New Jersey was essential. A complex undertaking,it would be necessary to locate multiple regional sources of both living and historic AWC, sufficient inquality and quantity to provide the materials for compiling a viable and representative mean.

To begin, living AWC, preferably in the range of 200+ years old, had to be found and sampled,and compiled into a viable "live tree" master that would secure the outermost year of the chronology to2014. Older sources, especially historic structures, had to be located and sampled, and they had toprovide material of such quality and age that the individual "site chronologies" from these historicalbuildings (often of undocumented age) could overlap the earlier portions of the "live tree datingmaster" with, minimally, a statistically significant 50+ years. Furthermore, the various historic sites hadto be synchronized and overlapped with each other, in order to extend the master in an unbrokenchronological chain sufficiently far back in time to traverse the potential age of the Swedish Granary. Inshort, a sequential series of measurements had to be created, affixed in 2014 and continuinguninterrupted back to approximately 1550, a period covering the purported age of the Granary.

Following extensive planning, field work began in May, 2014. Accompanied by the project'scoordinating manager, Joseph Mathews of CCHS, and assisted by architectural historian Joan Berkeyand historical carpenter J.P. Hand, dendrochronologists William Callahan and Dr. Edward Cook mademore than 20 exploratory and operational sampling visits to the SW New Jersey region. Samples werecollected from multiple stands of living trees in state forests, from sub-fossil trees at various locations,and from more than 10 historic structures (see Table 1). Nearly a dozen additional structures werevisited and surveyed without being sampled.

The effort to establish the foundational master chronology, one based on living trees and thus

with each calendar year specified, succeeded due to the local knowledge, contact networks andthorough reconnoitering efforts of the personnel from CCHS, and a serendipitous meeting ofcolleagues. After contact with the NJ Parks and Forests department, Joe Mathews from CCHS locatedremnant old growth AWC in Peaslee Wildlife Management Area. Permission was granted, and multiplesamples were collected there by Callahan, Cook, et alia. During an informal conversation with NicoleDavi, a researcher at Lamont-Doherty Tree Ring Lab, Dr. Cook discovered that she and colleagues hadsampled some old growth AWC trees in NJ in 2000, and graciously she shared the measurements, someextending back to 1790, with the present AWC project. Together these efforts provided the necessarymaterial for an absolutely dated, live tree master chronology for the period 1788-2014.

Figure 1 shows the modern master created by this phase of the AWC project. It is operationallyrobust back to the 1820's, meaning that there are enough individual samples calculated into each year toproduce a statistically representative mean. Prior to that decade the number of sampled trees includeddeclines, and although currently several individuals are compiled into each of these earlier years, thenumber is insufficient to be considered rigorously representative statistically; before 1800 only threetrees contribute to the chronology. Nevertheless, this AWC master is the longest calendar-year-datedrecord of regional annual growth for the species Chamaecyparis thyoides ever developed.

Figure 1-----------------------------------------------------------------------------------------------------------------------------------------------------

Seq Series Time_span 1780 1800 1820 1840 1860 1880 1900 1920 1940 1960 1839 1859 1879 1899 1919 1939 1959 1979 1999 2019 --- -------- --------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 1 NIC01A 1848 2000 .50 .36 .37 .33 .55 .47 .47 2 NIC01B 1844 2000 .26 .38 .38 .47 .51 .56 .53 3 NIC01D 1851 2000 .46 .42 .32 .45 .30 .36 .36 4 NIC02 1891 2000 .52 .53 .55 .52 .54 5 NIC03 1891 2000 .38 .47 .45 .35 .37 6 NIC06 1909 2000 .60 .65 .35 .37 7 NIC07 1888 2000 .47 .54 .72 .70 .69 8 NIC12 1903 2000 .55 .55 .59 .60 9 NIC14 1933 2000 .49 .42 .43 10 NIC16 1902 2000 .22 .24 .30 .31 11 NIC20A2 1820 2000 .47 .53 .51 .37 .31 .18 .35 .37 12 NIC20C3 1790 2000 .12 .24 .35 .43 .38 .44 .34 .36 .36 .37 13 CPFF01A 1912 2013 .50 .60 .60 .41 14 CPFF01B 1891 2013 .17 .09 .17 .27 .40 15 CPFF03A 1788 2013 .11 .28 .53 .47 .48 .29 .38 .19 .29 .23 16 CPFF03B 1806 2013 .31 .51 .39 .37 .25 .36 .39 .43 .33 17 CPFF05A 1863 2013 .39 .42 .55 .54 .51 .31 18 CPFF05B 1894 2013 .54 .52 .55 .50 .40 19 CPFF06B 1794 2013 .34 .33 .28 .34 .32 .36 .35 .41 .38 .32 20 CPFF07A 1911 2013 .61 .55 .56 .45 21 CPFF08A 1913 2013 .56 .53 .45 .39 22 CPFF09A 1903 2013 .60 .70 .64 .52 23 CPFF09B 1891 2013 .54 .54 .57 .57 .44 24 CPFF10A 1904 2013 .50 .51 .52 .42 25 CPFF10B 1862 2013 .54 .61 .60 .58 .46 .36

1

1.5

1780 1820 1860 1900 1940 1980 2020

Indi

ces

Time in Calendar Years

AWC Modern Master for Southern New Jersey

========================================================================================Figure 1. Regional Atlantic White Cedar (Chamaecyparis thyoides) dating master for Southern New Jersey covering 1788-2014. To be serviceable for dating historical structures and objects for the entire European settlement period in the region,this chronology must be robustly supplemented and extended from its present length to 1550 or before.=========================================================================

In spite of the important success in establishing this regional live tree master, from the broaderperspective of the AWC project the result remains incomplete. The length in years of the chronologyalready demonstrably overlies the normal extent of the natural age expectancy of regional AWC, yet

simultaneously it remains insufficiently long and robust to permit most dating of historical AWCmaterials from the early settlement through the post-Revolution era.

As discussed previously, in order to expand the length of master chronologies to years beyondthose of living trees it is necessary to assemble substantial amounts of older materials, identify andcorrelate any examples that overlap with the live tree master and/or with each other, and sequentiallybuild a continuous series of measurements backward in time. Very rarely does this stage produce rapidprogress, since much exertion often leads to no result, and in practice the effort generally isexceedingly demanding of time, resources, and patience. Requisite materials -the right species, theappropriate potential age, satisfactory physical condition, etc.- can be difficult or impossible to locate,and available materials may prove only after much laborious collection and analysis to be qualitativelyor methodologically unsuitable.

As they had in the search for living AWC trees, the associates from CCHS provided efficient aidin advancing the project. Familiar with local geography and building history, they were able tocompose a list targeting potentially useful structures and objects throughout the region. Over a periodof several months Callahan & Cook visited these sites, surveyed and sampled them whenever the AWCmaterial was judged promising (see Table 1). In all, several dozen locations were inspected, andsamples of disparate number and quality were acquired from perhaps half of these. Not all the collectedspecimens could be utilized, as ultimately many were rejected after examination in the laboratory dueto the poor physical quality of the wood, and/or because they had too few rings to ever reliably supportstatistical evaluation: under normal circumstances approximately 60 rings are required to meet minimaldendrochronological protocols.

Table 1-----------------------------------------------------------------------------------------------------------------------------------------------------

1) Moses Crossley House, Cape May Court House, NJ2) Caesar Hoskins House, Mauricetown NJ3) ۩ Veale-Sewall Cabin, Upper Hopewell, NJ4) Reeves-Iszard-Godfrey House, vicinity Seaville, NJ (originally Middle Township)5) ۩ Historical Society Museum Barn, Cape May Court House, NJ6) ۩ Swing Family Cabin, Mannington, NJ7) Seaville Quaker Meeting House, Seaville, NJ8) ۩ Stites Barn, John Gandy Homestead, vicinity Greenfield, NJ9) ۩ Falkenburge Barn, South Dennis, NJ10) Schorn Cabin, Swedesboro, NJ11) Hope House, vicinity Nesco, NJ12) Richard Townsend House, Middle Township, NJ13) Penny Watson House, Greenwich, NJ14) Fred Peech Barn, Marmora, NJ15) Inn at Historic Cold Spring Village, Lower Township, NJ (originally from Dennisville, NJ)16) Swedish Granary, Greenwich, NJ (originally Lower Hopewell Township)

========================================================================================Table 1: Historical sites and structures from throughout south and south-central New Jersey providing AWC wood materialfor laboratory analysis. Not all source materials were of sufficient quality to allow subsequent laboratory processing.The symbol ۩ indicates sites included in the relative master chronology, see Figure 2 and Table 2.========================================================================================

Fortunately, several selected historical sites provided material of sufficient quality that theindividual timbers could be synchronized with each other and their measurements thereafter combinedinto a unified "site chronology". Because they still cannot be assigned specific calendar years they aredesignated as "floating" or "relative chronologies", but they remain extremely useful for crossdatingpurposes. As mathematical means, such compilations tend to significantly strengthen the statistical

"signal" so that the new combined site chronology more closely reflects actual growth conditions thandoes any single individual timber.

Although the selected site series remain undated absolutely, i.e. none of the sites is dated to aspecific year, they all have purported dates suggesting construction in either the 18 th or early 19th

centuries, and therefore were considered as potentially contemporaneous and were tested to discern anyrelative overlap. Strong positive correlations between these buildings were discerned and the relativeoffsets in the outer, relative dates between buildings were not inconsistent with expectations based onevaluations of the buildings by architectural historians.

Table 2 shows the statistical strengths of the crossdating of the five buildings purportedlyconstructed in the mid-to-late 18th century and the early 19th century. Each site chronology is based onthe average of the measurements of two or more sampled timbers from the site that crossdate amongstthemselves. By first crossdating each building internally, independent of the other structures, aconstraint is imposed on the temporal placements of the different series. The numbers are expressionsof the "r-factor”, the Spearman rank correlation coefficient. This coefficient is a universally standardmeasure of relative statistical agreement between two groups of measurements or data. It can rangefrom +1 (perfect direct agreement) to -1 (perfect opposite agreement). These statistical correlations,produced by the COFECHA computer program, indicate how well each sample crossdates at variouspositions with the mean of the others in the group. The correlations listed vary in statistical strength,but all are within a range expected for correctly crossdated timbers from the eastern United States.

Table 2-----------------------------------------------------------------------------------------------------------------------------------------------------

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Correlations of 30-year dated segments, lagged 5 years1 2

3 No. with 995 1000 1005 1010 1015 1020 1025 1030 1035 1040 1045 1050 1055 1060 10654 Seq Series Time_span Years Master 1024 1029 1034 1039 1044 1049 1054 1059 1064 1069 1074 1079 1084 1089 10945 --- -------- --------- ----- ----- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----6 1 AWCSFC 997 1077 81 0.492 .46 .40 .42 .41 .38 .54 .56 .55 .71 .71 .57 .557 2 AWCVSC 983 1080 98 0.497 .51 .42 .47 .52 .53 .56 .65 .67 .62 .54 .47 .38 .33 8 3 AWCCMM 1000 1090 91 0.465 .26 .37 .39 .43 .51 .69 .70 .66 .66 .64 .59 .51 .45 .44 9 4 AWCGSB 1027 1093 67 0.484 .53 .55 .76 .61 .55 .54 .49 .40 .28 10 5 AWCFKB 1021 1102 82 0.362 .24 .38 .51 .53 .52 .46 .43 .42 .39 .3711 --- -------- --------- ----- ----- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 12 13 AWCSFC: Swing Family Cabin; AWCVSC: Veale-Sewall Cabin; AWCCMM: Cape May Museum Barn;AWCGSB: Stites Barn, John Gandy Homestead; AWCFKB: Falkenburge Barn========================================================================================Table 2. Output from COFECHA program showing the statistical strength of crossdating between five independentlydeveloped Atlantic White Cedar (AWC) site masters. The building names corresponding to the series codes are given at thebottom of the table. Spearman rank correlations between each ‘floating’ master and the mean of the site masters are shownfor 30-year periods with five year, 25-year overlaps. The years assigned are arbitrary (hence ‘floating’) because no calendaryear dates could be assigned by crossdating with a calendar year dated AWC master. However, the offsets of the years ofoverlap between buildings are generally consistent with purported construction dates based on historical assessments, circa1700-1775.========================================================================================

The black curve in Figure 2 illustrates the composite relative master created from the historicalsites during this phase of the AWC project. The statistical correspondences of the crossdating of theindividual sites in the composite are as listed in Table 2. Key signature years representing uncommonlynarrow ring measurements found in each of the five site chronologies also are indicated in the figure.Together with Spearman rank correlations, these signature years provide the base alignments for thecrossdating. The dearth of key signature years and the marked visual differences between theoverlapping chronologies are a stark graphical demonstration of the difficulties that have been, andprobably routinely will be, experienced in crossdating AWC historical structures in South Jersey.

Additional evidence of the methodological challenges confounding the AWC project is that onlythree of the site chronologies statistically correlate with a t-statistic above the desired t>3.5, the

standard minimum threshold for statistical crossdating. The "t-value" is Student's distribution test fordetermining the unique probability distribution for the “r factor”, i.e. the likelihood of the “r factor”correlation value occurring by chance alone. As a rule, a t=3.5 has a probability of about 1 in 1000, or0.001, of being invalid. Higher “t” values indicate exponentially increasing, stronger statisticalcertitude.

Two correlations exceed >4.0: that is, between AWCSFC and AWCVSC (t=4.9) and betweenAWCGSB and AWCFKB (t=4.2); only one other pair of chronologies crossdates with a t>3.5: that is,between AWCVSC and AWCGSB, (t=3.7). However, when AWCSFC and AWCVSC were combinedinto a experimental composite, crossdating between this alternative compilation and AWCCMM andAWCGSB then exceeded the t>3.5 threshold (t=4.0 and t=3.9, respectively). This exemplifies thebenefit of sequentially building multiple-site, regional master chronologies for crossdating. However, aproject of such thorough breadth requires much effort and time to accomplish, as multiple alternativeconfigurations must be systematically formulated, tested, rejected or accepted, then supplemented andadjusted with new alternative configurations, which in turn are tested, and so forth.

Figure 2----------------------------------------------------------------------------------------------------------------------------

0

0.5

1

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980 1000 1020 1040 1060 1080 1100

A W C S F CA W C V S CA W C C M MA W C G S BA W C F K BA V E R A G E

Indice

s

Relative Time in Years

AWC Cross-Dating Between Five Independent Buildings andthe Regional Average Series w/ Signature Years Indicated

Average Correlation (RBAR) Between the Five Buildings[30-year running means w/ 29-year overlaps]

Relative Time in Years

RBAR

1020 1040 1060 1080

t=4.9

t=4.2

RBAR=0.42

AWCSFC: Swing Family Cabin; AWCVSC: Veale-Sewall Cabin; AWCCMM: Cape May Museum Barn; AWCGSB: Stites Barn, Gandy Homestead; AWCFKB: Falkenburge Barn=========================================================================Figure 2. Illustration of crossdating between the five different historical site chronologies described numerically in Table 2.The building names corresponding to the series codes are given at the bottom of the table. Shared key signature years aremarked with a dotted vertical line. The t-value notation indicates the strength of correlation between specific selected sites.The series at the bottom -the black curve- is the composite, relatively dated AWC historical master for southern New Jersey,as presently configured. It is expected to serve as the basis for continued AWC chronology development in the future, withthe intention of eventually connecting the absolutely-dated live tree chronology and the relatively-dated site chronologiesinto a continuous master chronology functionally serviceable for dating AWC structures and artifacts over the entirety of thehistorical period.=========================================================================

Remarks

In order to apply dendrochronological dating methods it is necessary to possess a masterchronology for the species and region under study. In the case of the Swedish Granary in Greenwich,NJ, the lack of such a reference precluded all possibilities of using tree-ring analysis to date thebuilding when it was initially tested in 2008. The primary structural timbers used in its constructionwere of Atlantic White Cedar, a species not compatible with existing oak and pine historical masters. Inthe hope of using dendrochronology to date the Granary and other AWC buildings of New Jersey, theCumberland County Historical Society initiated a grant funded project in 2013 to create this master.

To construct a statistically robust master chronology is a scientifically complicated andtechnically demanding undertaking. Nevertheless, in a remarkably short time and with restrictedresources, unprecedented progress has been made. A modern AWC master chronology, affixed in timeby sampling live trees in the region, now exists for the period 1788-2014. Moreover, a collection ofseveral "relative" AWC chronologies has been assembled from sampled historic buildings and objects.Though not yet dated to specific years, their purported dates suggest that collectively they likely can beassigned to the period circa 1700-1790. At a minimum their existence is additional proof that historicaldating of the species is practicable, and they provide the foundation for future efforts to extend themaster chronology back in time.

Despite this success, the conjunction of the absolute and relative chronologies remainsunachieved. Because of a deficiency of materials from the period bridging these modern and historicalseries, no robust composite can yet be compiled. The material available is deficient in both number andquality. In order to extend the extant AWC masters and thereby establish a continuous chronologyviable over the entire settlement period, it will be necessary to: 1) find more buildings and artifactsconstructed of AWC, cut during 1750-1850, to correlate with the inner portion of the live tree datingmaster, and which also offer enough rings to bridge the gap between the dated master and variousundated site masters; 2) find in the landscape remnant AWC logs from trees that died decades ago, so-called sub-fossil material, and sample these for eventual addition to the dating master.

No buildings from the late 18th through mid 19th centuries containing AWC of suitable qualityhave been identified and sampled, but it is hoped that with time, exploration, and advertising some maybe found. Experience hereto has been that the latest structures to contain sizable AWC timbers wereconstructed by the first decade of the 1800's. As a consequence, living trees with 250+ rings wouldhave had to be available in order to have sufficient overlap with the ring series from the historicstructures. None so old have been found, apparently because intensive harvesting of AWC forconstruction during the colonial era had exhausted supplies of old-growth AWC in the region. Ofcourse, old trees may still exist in the forests, but a search will require much more exploration than thetimetable and funding of this project allowed.

Two large AWC logs lying on the surface of a coastal salt marsh were sampled. Each of theselogs had over 200 rings but neither crossdated with the dating master shown in Fig. 1, nor did theycrossdate with any of the collected historical samples. Remarkably, the logs did not crossdate with eachother either. Although in a similar location and visibly in similar states of physical preservation, theirages in fact may be very different from one other, perhaps by hundreds of years. Logs of this kind canserve as a valuable source of rings and should be sought, for if enough are found some will contributeto extending the master chronologies, potentially back centuries into pre-settlement times.

Although much has been accomplished, one goal of the AWC project remains unfulfilled:successfully dating the Swedish Granary. Repeated attempts to correlate the Granary with the modernchronology and/or site chronologies have procured no viable result. Reasons for this are purelyspeculative at this time. It is possible that the age of the building in fact is as proposed by somearchitectural historians, i.e. in the later part of 17th century, in which case it lies outside the presentrange of existing chronologies. Another potential explanation is that it is similar in age to tested

historical sites, i.e. post-1700, but that the signal of its internal site chronology is statistically too weakor anomalous to correlate at present with any existing masters; the compiled mean chronology for theGranary timbers contains in toto just 69 rings, a not overly large number if synchronizing with othernon-robust tree ring series. Alternately, the Granary could be from the 18th century or even the 19th

century, and the same conditions of statistical weakness could preclude crossdating under currentcircumstances.

It seems very likely that the Swedish Granary ultimately can be dated successfully usingdendrochronology. Experience from the recently completed stages of the investigation proves thatAWC can crossdate and that master and site specific chronologies can be compiled thereafter. However,creating a wholly new operative dating chronology for a previously untested species requires resourcesand patience. It took A.E. Douglass seven years to finalize the master chronology that enabled him todate the Anasazi dwellings in the American Southwest. The historical master chronology for oakcompiled by Cook & Callahan had its beginnings in eastern forests in 1984 and was not fully functionaluntil 1992. In comparison, since the active field sampling phase of the AWC project began in summer2014 it has proceeded with extraordinary speed and efficaciousness. The results are very promising.

Edward Cook was born in Trenton, New Jersey, in 1948. He received his PhD. from the Tucson Tree-Ring Laboratory ofthe University of Arizona in 1985, and has worked as a dendrochronologist since 1973. Currently director of the Tree-RingLaboratory at the Lamont-Doherty Earth Observatory of Columbia University, he has comprehensive expertise in designingand programming statistical systems for tree-ring studies, and is the author of many works dealing with the variousscientific applications of the dendrochronological method.

William Callahan was born in West Chester, Pennsylvania, in 1952. After completing his military service he moved toEurope, receiving his MA from the University of Stockholm in 1979. He began working as a dendrochronologist in Swedenin 1980 at the Wood Anatomy Laboratory at the University of Lund, and returned to the United States in 1998. A formerassociate of Dr. Edward Cook at the Tree-Ring Laboratory of Lamont-Doherty, he has extensive experience in usingdendrochronology in dating archaeological artifacts and historic sites and structures.