Dendrochronology

Date 2022

Event ID 1166205

Category Scientific Dating

Type Dendrochronology

Permalink http://canmore.org.uk/event/1166205

NS 79173 93674 Historic conifer timbers which had been removed by the main contractors from the roof of Cowane’s Hospital during major repair works were triaged in 2019 for their dendrochronological potential. Their Stage 1 assessment was commissioned in 2020, which led to their Stage 2 analysis in 2022.

A selection of 25 conifer timbers, mostly sarking boards and a few beams, were selected for detailed recording and sampled for dendrochronology and species identification. This revealed a mix of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) amongst both boards and beams, most of which had been sawmilled. Woodworking analysis showed the majority of boards had suffered from warping and had been corrected with adze and axe prior to their use on the roof. Once laid on the roof, the sarking boards were augured to take oak (Quercus sp.) pegs to hold the slates on. These pegged sarking boards were termed Type A boards and included both Scots pine and Norway spruce examples. Norway spruce is not native to Scotland and this immediately indicated the probable use of imported timber.

Many of the samples were very slow grown and heavily wood-

wormed at the outer edges, making this a challenging assemblage to date. Dendrochronological analysis of 22 samples allowed eight pine timbers (7 Type A boards and 1 beam) to be cross-matched into a site chronology and dated. While most edges were heavily axe-trimmed, the bark edge survived on two pine boards made from trees felled in the late 1630s (winter felling in 1637–8 and 1638–9 indicated) in southern Norway, matching most closely with reference data from the Agder region, as has been the case for other analysed 16th- and earlier 17th-century conifer timbers from buildings around the Forth Estuary. Cowane’s Hospital currently represents the latest date for this pine timber source being used in Scotland.

Two Norway spruce Type A boards were tentatively dated to a winter 1639–40 felling in the same source region. Thus nine of the 16 Type A boards and one beam were dated. The other Type A boards must be from the same primary phase based on their woodworking evidence but either had lower ring counts or intractable tree-ring sequence measurement difficulties preventing dendro-dating. Four other boards were not Type A, all were milled Scots pine, with nails and no pegs, and while they could not be dated, they appear to be later replacement sarking.

The majority of analysed timbers were demonstrated to be from the original 17th-century fabric. Documentary research by John Harrison has shown the process of building Cowane’s Hospital began in 1637 with the demolition of the previous building on this site. Building supplies were being brought to the site over several years thereafter, including a large shipment of ‘deals’ (boards) and ‘trees’ (beams), brought into Alloa in July 1641 by a Norway skipper, which was then floated up the Forth to Stirling. At least some of the dendro-dated timbers are likely to have been part of that particular shipment. The project has furthered our understanding of woodworking and the timber supply in 17th- century central Scotland and has provided important new tree- ring data, including the first ever data set for Norway spruce in Scotland, which will assist in dating timbers in other buildings of this period. These results are considered in detail in the Stage 1 and Stage 2 project reports.

Archive: NRHE (intended)

Funder: The Patrons of Cowane’s Hospital Trust

Coralie Mills – Dendrochronicle

(Source: DES Volume 23)