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Dendrochronology: How Old is It?

When looking at an old building, it can be difficult to determine the age of a building. The building’s construction materials and decorative elements like trim, mouldings, and windows can provide a date range of of when it was built. Some buildings like stone farm houses, churches, or public buildings may have dates marked on their exterior. Cornerstones, carvings on mantle pieces or exterior brick walls might record a specific year.  Another way to date a building is through paper records like deeds and local government property records, although these may not be accurate, and typically are for more recent properties. 

Most buildings do not have visible dates and many have been altered to meet the needs of their owners, so that an accurate date is difficult. Another way of dating a building is through dendrochronology analysis. This is the case for the Morgan Log House. Originally, it was thought that the current house dated to the late seventeenth century and was occupied by the Morgan family who owned the land. However, a dendrochronology study was done in 2000, which resulted in the determination that the house was likely constructed in the 1770s, likely by the Yeakle or Cassel families, who owned the property after the Morgan family. These kinds of studies can provide insight into a building’s age if it is unknown by paper records. Many people may not be aware of this kind of study so the museum thought a blog post might enlighten those interested!

Dendrochronology is the study of trees and their rings to determine the age of a tree when it was felled or cut down.  Large visible vessels or rings in the tree’s trunk indicate the spring season and the rings can indicate how wet or dry the seasons were. The study of the Morgan Log House was completed by William J. Callahan and Dr. Edward Cook. 

For the Morgan Log House, the majority of the woodwork in the house is oak with some of the replacement wood pieces of softwoods. Nine samples were taken of the interior of the house with six determined to be viable. These samples needed to be in good condition that had the “bark edge” or the layer that formed last under its bark. Samples were taken at the sill log cellar stairwell, store room landing, west lintel support, fireplace lintel, summer beam, and the south wall of the attic. These samples, compared to the Philadelphia geographic region’s wood, indicate that the trees used in the construction of the log building were felled or cut in the 1770s, after 1767 and before the 1780s. This result indicates that the log house was likely constructed during John Yeakel or Yellis Cassel’s ownership. No samples were taken of the support beams of the frame wing that was rebuilt in the 1970s, which have an old appearance and were hewn with an axe or adz. Additional research and testing may provide additional information as to the age of the wing’s beams. It may be what remains of the Morgan family occupation or a later addition to the circa-1770 log house.

To learn more about dendrochronology, please visit PBS’ page and watch a video  explaining the process: http://www.pbs.org/time-team/experience-archaeology/dendrochronology/.