Testing of samples

The timbers from the bridge were dated by using radiocarbon dating. This is technique that uses the fact that all living things, including trees, take in the carbon 14 isotope from the atmosphere during their lives. After they die they emit this isotope at a steady rate. By measuring the amount of C14 left in the object, this can give us an approximate age.
 
We know from tests carried out by the Queen’s University of Belfast Radiocarbon Dating Laboratory this that it is highly likely the bridge at Testwood Lake dates to 1500BC.
 
We can also date timber from the sequence of tree rings shown in the wood. Each year a tree will grow a certain amount depending on how good the growing conditions were that year – a good year will produce a thick tree ring, and a bad one a thin ring. The pattern of rings can be matched against a known sequence to establish the date the tree was cut down.
 
In the case of the Testwood Lakes samples, the tree used was 137 years old when cut down, and the sequence of 137 tree rings could be compared with those obtained on the bridges at Meadow Lake.