An example of a tree cross-section and the type of wood sample University of Florida and University of Tennessee researchers extracted from the Ximénez -Fatio house in St. Augustine, Fla. sit on an antique table in the historic building. The researchers used such wood samples to accurately date a second-story addition to the building – proving that the technique can be used effectively in the southernmost part of the United States. The researchers showed the addition was built in the late 1850s, several decades later than historians had believed. UF/IFAS Photo by Tyler Jones.