Summary
A total of seven samples was obtained from a series of ceiling joists in the ground floor room at the east end of this building. The analysis of these samples produced a single site chronology consisting of six samples having a combined overall length of 140 rings. This site chronology was dated as spanning the years 1478 to 1617. Interpretation of the sapwood, and the relative positions of the heartwood sapwood boundaries on the dated samples, would suggest that all of them represent timbers with a felling date of 1617.

Sampling

The house at 61 Long Acre, Bingham contains several main beams and smaller timbers. These are principally two large east-west bridging beams in the ceiling of the ground-floor rooms, from which run a number of north-south common joists. There are other timbers forming wall timbers, or possibly cross-rails, or door heads, but these are smaller, and are less accessible being buried within the brickwork of the walls. Most of the ceiling timbers appear to be integral to the construction and there are no obviously reused timbers amongst them. The roof of the house has been long replaced and nothing can be said of its original form. It is known that there are additional timbers in the adjoining property which is likely to have been part of the same construction.

Thus, samples were obtained from seven different, apparently original, timbers, each sample being given the code BNG-A (for Bingham, site "A") and numbered 01 - 07. The position of these samples was recorded at the time of sampling on a drawn plan. Details of the samples are given in Table 1. In this Table, as in the plan, the trusses and their constituent timbers have been numbered and described on a site north to south, or east to west basis, as appropriate. For the purposes of the plan and Table the front of the house is taken to be facing south, the rear to be facing north.

Tree-ring dating

Tree-ring dating relies on a few simple, but quite fundamental, principles.
Firstly, as is commonly known, trees (particularly oak trees, the most frequently used building timber in England) grow by adding one, and only one, growth-ring to their circumference each, and every, year. Each new annual growth-ring is added to the outside of the previous year's growth just below the bark. The width of this annual growth-ring is largely, though not exclusively, determined by the weather conditions during the growth period (roughly March - September). In general, good conditions produce wider rings and poor conditions produce narrower rings. Thus, over the lifetime of a tree, the annual growth-rings display a climatically determined pattern. Furthermore, and importantly, all trees growing in the same area at the same time will be influenced by the same growing conditions and the annual growth-rings of all of them will respond in a similar, though not identical, way.

Secondly, because the weather over any number of consecutive years is unique, so too is the growth pattern of the tree. The pattern of a short period of growth, 20, 30 or even 40 consecutive years, might conceivably be repeated two or even three times in the last one thousand years. A short pattern might also be repeated at different time periods in different parts of the country because of differences in regional micro-climates. It is less likely, however, that such problems would occur with the pattern of a longer period of growth, that is, anything is excess of 50 years or so. In essence, a short period of growth, anything less than 50 rings, is not reliable, and the longer the period of time under comparison the better.

The third principal of tree-ring dating is that, until the early- to mid-nineteenth century, builders of timber-framed houses usually obtained all the wood needed for a given structure by felling the necessary trees in a single operation from one patch of woodland or from closely adjacent woods. Furthermore, and contrary to popular belief, the timber was used "green" and without seasoning, and there was very little long-term storage as in timber-yards of today. This fact has been well established from a number of studies where tree-ring dating has been undertaken in conjunction with documentary studies. Thus, establishing the felling date for a group of timbers gives a very precise indication of the date of their use in a building.

Tree-ring dating relies on obtaining the growth pattern of trees from sample timbers of unknown date by measuring the width of the annual growth-rings. This is done to a tolerance of 1/100 of a millimeter. The growth patterns of these samples of unknown date are then compared with a series of reference patterns or chronologies, the date of each ring of which is known. When a sample "cross-matches" repeatedly at the same date against a series of different relevant reference chronologies the sample can be said to be dated. The degree of cross-matching, that is the measure of similarity between sample and reference, is denoted by a "t-value"; the higher the value the greater the similarity. In turn, the greater the similarity the greater is the probability that the patterns of samples and references have been produced by growing under similar conditions at the same time. The statistically accepted fully reliable minimum t-value is 3.5.

However, rather than attempt to date each sample individually it is usual to first compare all the samples from a single building, or phases of a building, with one another, and attempt to cross-match each one with all the others from the same phase or building. When samples from the same phase do cross-match with each other they are combined at their matching positions to form what is known as a "site chronology". As with any set of data, this has the effect of reducing the anomalies of any one individual (brought about in the case of tree-rings by some non-climatic influence) and enhances the overall climatic signal. As stated above, it is the climate that gives the growth pattern its distinctive pattern. The greater the number of samples in a site chronology the greater is the climatic signal of the group and the weaker is the non-climatic input of any one individual.

Furthermore, combining samples in this way to make a site chronology usually has the effect of increasing the time-span that is under comparison. As also mentioned above, the longer the period of growth under consideration, the greater the certainty of the cross-match. Any site chronology with less than about 55 rings is generally too short for satisfactory analysis.

Analysis

In the case of the seven samples from 61 Long Acre each one was prepared by sanding and polishing and the growth-ring widths of all of them were obtained by measuring. It will be seen from Table 1 that the number of rings on a couple of these samples is a little low, and that the number of rings on one sample, BNG-A06, is below the statistically reliable minimum. However, the growth-ring widths of all seven samples were compared with each other. This comparative process resulted in six of the seven cross matching with each other at relative positions as shown in the bar diagram. Because of the cross-matching between them the growth-rings of the six samples were combined at the relative off-set positions shown to form a site chronology, BNGASQ01, with a combined overall length of 140 rings. Site chronology BNGASQ01 was then compared with a wide range of reference chronologies for oak. In this process it consistently and reliably cross-matched with a high number of them when the date of the first ring of the site chronology is 1478 and the date of its last measured ring is 1617. The evidence for this dating is given in the t-values of Table 2. The list included with a few major and wide-ranging national reference chronologies. It then lists several more local chronologies. The standard of the cross-matches is well above the significant minimum t-value of 3.5.

Interpretation

Having obtained a date span for site chronology BNGASQ01 as a whole, it is now possible to calculate the date span of each individual sample. From this, and using the sapwood on each sample, it becomes possible to make some interpretation as to the felling date of the timbers represented and the construction date of that part of the building in which the timbers are found. Normally, and unfortunately for dendrochronology, the sapwood element of trees is rather soft and it is most often lost, totally or at least in part, from the timbers. This is often done either by the original carpenters but also through woodworm, decay and general abrasion. In the case of the samples from 61 Long Acre, however, not only do most of the samples at least retain the heartwood/sapwood boundary (denoted by "h/s"), but also happily one of them, BNG-A02, retains complete sapwood. This means that the sample has the last ring produced by the tree before it was cut down. This situation is denoted by "C" in Table 1 and the bar diagram.
In this case sample BNG-A02 has a last (complete) sapwood ring date of 1617. The relative position of the heartwood/sapwood boundaries on the other dated samples all lie close to each other, varying by only a couple of years. This consistency is highly indicative of a group of trees having the same felling date, and it is almost certain that all the timber used in this phase of the building were felled at one and the same time, 1617.

Conclusion

Samples were obtained from seven different timbers at 61 Long Acre, Bingham. All the timbers sampled appeared to be integral to each other, and appeared to belong to the same phase of building. Six of the seven samples obtained were combined to make a very satisfactory site chronology of overall length 140 rings. One of the samples retains complete sapwood having a last measured ring date of 1617. It is highly likely that this represents the felling date of all the other timber in this phase of the building and indicates that construction took place very soon after this time.