Core sample dating
His laboratory is still one of the leading centres in world dendrochronology.
It was not until 1939 that the science was taken seriously in Europe, mainly through the efforts of Professor Huber in Germany, and not until after World War II that such studies became established in the UK.
In order to obtain an accurate match and hence a date, it is important to have at least 80 rings on the specimen that is to he dated.
With fewer rings the pattern might have repeat matches at different points in the time scale and so give rise to multiple possible dates.
He established a laboratory in the university of Arizona, at Tucson, to study tree-rings.
Year by year the trees throughout the region produce a similar pattern of wide and narrow rings in response to the weather changes.
It is this pattern that allows the accurate dating.
If research into other sources of information also fails to throw light on the building's history, resort may be made to the various scientific methods of dating.
This article outlines three of the most important methods currently used for dating buildings or, in a complex situation, the order of construction within the building.
Almost certainly the century or portion of a century when it was built may be assigned with some certainty.