If this were so, the width of the annual growth rings would show changes in synchronism with the sunspot numbers.
None is infallible and before embarking on an extensive dating survey, due thought must be given to what might be achieved and which methods might be the more successful. Whilst earlier types of wooden joints may be copied in later buildings and earlier styles may be reintroduced in later periods to confound the conservationist or historian, any reuse of older materials should become obvious by the use of the chronometrical methods described here.The incorporation of ancient bog oak into a building, no matter how intricately carved or jointed, would immediately become obvious to the chronologist, as would timber renovations.Dendrochronology is the oldest method, having been introduced over a century ago by an American astronomer, Professor A E Douglass.He wanted to know whether the number of sunspots affected weather on Earth.Upon encountering a new site, the archaeologist immediately requires information about its age in order to set it in context with other sites.In research into our heritage the conservationist or architect may be able to date the general period of a building he is working with from either the situation, materials of construction, type of timber joints or other stylistic features.
Almost certainly the century or portion of a century when it was built may be assigned with some certainty.
However, as more and more work is done and increasing numbers of structures with complex constructional phases are encountered, the general features may not be sufficient to give the accuracy in dating that is currently required.
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.
These are: dendrochronology (or 'tree-ring' dating), radiocarbon dating and thermoluminescence dating.
Each method has a distinct role in the investigation of historic buildings.