#35 - Dendrochronology and the Ryves Holt House

 So far on my escapades to learn the age of the Ryves Holt House in Lewes I have used a lot of secondary sources and a few primary sources. Basically, I have kept looking for answers in books. But what about other tools? I hope to be able to work on a structural analysis of the RHH in the future where I could discover evidence for the construction chronology, and I also hope to be able to collect photographs to track modern alterations to the building. But what if I told you there was a way to use the wooden structural beams to give a guess at age? That’s right, this week it's dendrochronology time!

Dendrochronology is the use of tree rings to date a piece of wood. If a large enough sample of wood from the same species of tree can be gathered, including both cut timber and living trees, then by comparing the size and number of rings you can figure out a chronology through time. Tree rings vary in size depending on season and weather conditions, so they can be lined up from trees that may not have been alive at the same time, as well as to identify the age of cut wood from the inner remaining rings. 

I have used dendrochronology for another project. In graduate school I was smitten with Pueblo architecture and how they were constructed overtime. Because of the good preservation conditions in the Southwest, they have an extremely detailed dendro record to use for dating structural members. They can be so specific as to tell when a timber was reused in a new place with remarkable accuracy. Maybe more on that later, dear reader.

As for the Ryves Holt House, the company Dendrochronology, Inc. was hired to gather samples and attempt to date timber from the house. This was possible because White Oaks are plentiful in the Chesapeake Bay area and they are both long lived and able to survive well inside buildings. The testing was done in October 1988 and December 1989, and they discovered that likely the wood from the original part of the house dates from 1665 with little to no evidence that the wood was set out for a time. This means that structural members of the original portion of the RHH completed the growing season of 1665, then were cut down and almost immediately used in the RHH.

Sounds great, right? The Lewes Historical Society says the RHH is from 1665 and the dendrochronological testing agrees, I solved it, yes? Not just yet. The LHS uses this report to claim the age of the building. But there are plausible holes in the argument. 

First, dating was only done on 7 samples. Now, they did take 55 samples, but it is definitely likely that some were not suitable for dating - too degraded, contaminated, not white oak, etc. Still, I am not convinced that 7 samples is a large enough group to determine both the date and the idea that the wood was cut down and immediately used. I think more samples could help to better determine this, either by creating more positive dates of 1665 or by gathering more evidence that the wood was not seasoned for a significant period of time.

Second, the testing was done in the 1980s. I would like to see new samples taken and dated, perhaps in the intervening thirty years their sample sizes have grown and would make new dating tests more accurate. 

Third, the report itself recommends more testing to have a greater sample size, but also to test the newer additions to understand the construction phases better. This would help to build a construction chronology and make sure to survey any anomalies in conflicting dates. We would be able to see more clearly how the house was built, which walls came first or were moved, etc.

Fourth, and most importantly, just because the wood dates from 1665 does not mean the house was built in 1665. Despite lack of evidence, the structural timbers could have been left out in the weather for a time. Or perhaps the timbers were reused from another building. After all, one of the big sticking points for me to believe the 1665 date is that would mean the RHH had to have survived the Lord Baltimore Raids in the 1670s. An older building could have been destroyed and its surviving beams then used to build the RHH. I wonder if a more in depth analysis of the structural timber would show any fire damage to the original beams. Or, even if unlikely, perhaps Dendrochronology, Inc. failed to find the oldest beams in the RHH and there could be some timber that predates 1665! 

Right, so this report from Dendrochronology, Inc. in 1990 shows that there are timbers in the RHH that completed the growing season of 1665. This means that there is a very good chance that the building was built in 1665 or soon thereafter. It does not unequivocally state the construction date of the RHH as 1665, however. This report, though, can be used as one piece of evidence to anchor the age of the RHH in the latter half of the 17th century, which is still very old for surviving buildings of the Mid-Atlantic.