Dendrochronology: Using Tree Rings to Answer Questions about the Pavilion’s Past

The Pavilion at Fort Ticonderoga.

The Pavilion at Fort Ticonderoga.

In the summer of 2013 with support from the National Trust for Historic Preservation, Fort Ticonderoga began an in-depth study of the structural history of the Pavilion.  Oral history tells us that the Pavilion was built in 1826 by William Ferris Pell and occupied by his family until about 1840.  From the early 1840s through the end of the 19th century, the house served as a hotel.  When William Ferris Pell’s great-grandson, Stephen H.P. and his wife Sarah G.T. Pell began the restoration of FortTiconderoga in 1909, they simultaneously undertook the restoration of the Pavilion and then used the house as a summer residence for many years.  After Stephen Pell’s death in 1950, his son John occupied the house through 1987. As one of the earliest summer homes and hotels in the region, the Pavilion is one of the most important historic structures in the Adirondacks.

While the building’s occupation and use over the past 187 years is quite well documented, how the structure evolved over that period remains a mystery.  It is clear from historic photographs of the Pavilion that many elements of the building have changed.  Windows and doors have moved, appeared, and disappeared; porches have come and gone; and even a large portion of the building’s central structure was rebuilt over a century ago.  It is also possible that significant portions of the Pavilion were built over the course of several years.  But exactly when and why these changes occurred is largely unknown.  Clearly, there are several questions related to the Pavilion’s construction date(s) that need to be answered.

There are several ways of dating old buildings.  General dates can be estimated by simply examining interior and exterior decorative elements such as trims, mouldings, and window design.  These details can place a building’s construction in a general time span within about ten years or twenty years.  Some buildings have actual dates incorporated into their construction.  Cornerstones, dates carved in mantelpieces, dates formed of brick in exterior walls, or occasionally as wrought iron fixtures applied to a building’s façade suggest a more definitive year for a building’s construction.  Most buildings, however, do not have clear dates visible on their structure and many structures have been modified to the point where simple observation is not enough to reliably determine a date of construction.  Another option is dendrochronological analysis.

Core samples are about a quarter inch in diameter and as long as possible.  These samples contain between 30 and 60 growth rings.

Core samples are about a quarter inch in diameter and as long as possible. These samples contain between 30 and 60 growth rings.

Dendrochronology is a form of absolute dating that can be an indispensible tool for architectural historians.  The concept behind it is simple; take wood core samples from original timbers in a building’s framework and match the wood’s growth rings within a known chronology of growth rings from the same species of wood recorded in the geographic region where the building stands.  For dendrochronology to be most accurate the timber from which a sample is taken needs to be in good condition and have the “bark edge” of the tree still visible.  The bark edge is the last layer of wood that formed while the tree was still growing located directly underneath the bark.  In most cases early structures were built using timber that was still green meaning that if the date that the tree was cut can be established through dendrochonology, that same date is likely to be the year or within a year of the beginning of the construction of the building.

 

Dendrochronological Consultant William J. Callahan, Jr. uses an electric drill and specially-machined bits to extract cores of wood from structural timbers in the Pavilion.
Dendrochronological Consultant William J. Callahan, Jr. uses an electric drill and specially-machined bits to extract cores of wood from structural timbers in the Pavilion.

During the third week of November 34 wood core samples were extracted from structural timbers within the Pavilion.  The sampling was undertaken by Dendrochonological Consultant William J. Callahan, Jr. and the analysis will be undertaken by his colleague Dr. Edward Cook.  Mr. Callahan was very pleased with the samples and feels confident that they will yield good results.  This is the first such analysis ever undertaken at Fort Ticonderoga and the results are no doubt going to be very interesting.  While we are hopeful that the results will answer many questions about the date of the building, like any research, there may be just as many questions raised by the analysis as are answered.  So stay tuned, we are about to learn a lot about the Pavilion’s past!

 

Blog post by Christopher D. Fox, Curator Fort Ticonderoga

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