CANTERBURY, ENGLAND—BBC News reports that stained glass windows over the south entrance of Canterbury Cathedral, which depict the ancestors of Christ, have been re-dated to the mid-twelfth century using a new, non-destructive technique. Conservator Léonie Seliger and her colleagues used a device called a windolyser to shine a beam on the surface of the glass. Spectrometry was then used to analyze the chemical fingerprint of the glass and calculate its age. The new dates indicate that the windows may have been in place when Thomas Becket, Archbishop of Canterbury, was assassinated in the cathedral in 1170 by four knights who thought they were acting on the orders of King Henry II. Because the building was damaged by fire in 1174, it had been previously thought that the windows were crafted in the thirteenth century. “The scientific findings, the observations, and the chronology of the cathedral itself all fit together very nicely now,” commented art historian Madeline Caviness, who noted in the 1980s that the style of these glass panels suggested that they could be older than the cathedral’s other windows. To read about stained glass unearthed during excavations at Westminster Abbey, go to "Westminster Abbey's Hidden History."