CENTRE for ARCHAEOLOGY Centre for Archaeology Report 25/2001
Total Page:16
File Type:pdf, Size:1020Kb
S ("-1 1<. 6?r1 36325 a ~I~ 6503 ENGLISH HERITAGE Report 25/200 I Tree-Ring Analysis of Timbers from Gunns Mills, Spout Lane, Abenhall, Near Mitcheldean, Gloucestershire RE Howard, R R Laxton and C D litton CENTRE FOR ARCHAEOLOGY Centre for Archaeology Report 25/2001 Tree-Ring Analysis of Timbers from Gunns Mills, Spout Lane, Abenhall, Near Mitcheldean, Gloucestershire R E Howard, R R Laxton & C D Litton © English Heritage 2001 ISSN 1473-9224 The Centre for Archaeology Reports Series incorporates the former Ancient Monuments LaboratOlY Report Series. Copies of Ancient Monuments LaboratolY Reports will continue to be available from the Centrefor Archaeology (see back ofcover for details). Centre for Archaeology Report 25/2001 Tree-Ring Analysis of Timbers from Gunns Mills, Spout Lane, Abenhall, Near Mitcheldean, Gloucestershire RE Howard, R R Laxton & C D Litton Summary Fifteen samples from the timber portion of this blast furnace were analysed by tree-ring dating. This analysis produced a single site chronology of nine samples, the 244 rings it contains spanning the period AD 1438 - AD 1681. Interpretation of the sapwood, and the relative positions of the heartwoodlsapwood boundaries on the dated samples, suggests that the timbers represented, all from the northern half of the timber building, were felled in late AD 1681 or early AD 1682. This felling took place as part of a reconstruction programme, known to have taken place in AD 1682 3 and does not date to the cAD 1740 conversion of the building to a paper milL Keywords Dendrochronology Standing Building Authors' address University of Nottingham, University Park, Nottingham, NG7 2RD. Many CfA reports are interim reports which make available the results ofspecialist investigations in advance of full publication. They are not subject to external refereeing, and their conclusions may sometimes have to be modified in the light of archaeological information that was not available at the time of the investigation. Readers are therefore advised to consult the author before citing the report in any publication and to consult the final excavation report when available. Opinions expressed in CfA reports are those ofthe author and are not necessarily those of English Heritage. TREE-RING ANALYSIS OF TIMBERS FROM GUNNS MILLS, SPOUT LANE, ABENHALL, NEAR NnTCHELDEAN,GLOUCESTERSHIRE Introduction The Forest of Dean, to the west of the River Severn in Gloucestershire, has a long history of iron making, with evidence of workings dating to Roman times and possibly earlier. In the medieval period the industry expanded making the Forest one of the largest iron-producing areas of the country. By the end of the seventeenth century nearly half the furnaces working in England were located in this area. Of these Gunns Mills at Abenhall, near Mitcheldean (SO 675159; Figs 1 and 2), has been assessed as the best preserved example ofa seventeenth-century charcoal-fired blast furnace in the country; it is listed grade IT* and is designated a Scheduled Ancient Monument. It is believed that Gunns Mills dates at least from the early part of the seventeenth century; the Crown ordered the casting of610 guns in the area in AD 1629 and the name of the site may commemorate this undertaking. However it is perhaps more likely that the site is named after William Gunn, who was tenant of the site at the start of the seventeenth century. The first certain use of the site as a furnace is in AD 1634 when "Gunnes Mill" was listed in the ownership of Sir John Winter. In the later seventeenth century, after the Restoration, the Crown became increasingly concerned over the deforestation of the area and the AD 1667 Dean Forest (Reafforestation) Act cut off the fuel supply to the industry. Although, by the end of the eighteenth century coke fired blast furnaces were taking over; this new fuel was not used correctly in the Forest, leading to a decline in iron making in the area. The furnace at Gunns Mills may in fact have already gone out of use by this date, there being instructions to destroy the site in AD 1650 by order of the Parliamentary government. It is certainly recorded as being in ruins in AD 1680. The site was bought at this time by messers Hall and Soudamore who rebuilt the derelict furnace in AD 1682 - 3. This reconstruction work is recorded in the date stamped on the cast-iron upper lintel above the casting aperture. Production of iron continued intermittently at Gunns Mills through the early eighteenth century until AD 1736 when production ceased altogether. It is known from documentary sources that the buildings were then converted to a paper manufactory shortly before AD 1743. It is believed that at this time an additional timber-framed structure was placed on top of the existing masonry blast-furnace structure and used as a paper drying shed. In AD 1745 the site was tenanted by Joseph Lloyd, it remaining with the Lloyds until the paper works closed in AD 1879. After this time the building was used for agricultural purposes, this use lasting well into the twentieth century. It has been unused and abandoned since about AD 1960 and is once again in a ruinous condition, and in a dilapidated and dangerous state. Sampling and analysis by tree-ring dating was commissioned by English Heritage to inform a proposed programme of repair. The purpose of this analysis was to establish with greater certainty the construction date of the timber framed portion forming the top floor of the building. It was believed unlikely that it belonged to the original early seventeenth-century phase, but could possibly have been part of the reconstruction work undertaken in AD 1682- 3. It was believed, however, that the timber-framed structure most probably belonged to the mid eighteenth century work when the mill was converted to paper manufacture. The Laboratory would like to take this opportunity to thank Vicky Harmer of English Heritage, south-west region for assistance in arranging sampling at this site. The English Heritage brief describes Gunns Mills as containing three phases. Phase I consists of the c AD 1620s iron furnace and phase IT of the AD 16805 furnace rebuild; the brief states that neither of these two phases has any timbers remaining. Phase III consists of the timber-framed building built on top of the furnace and believed to be possibly oflate seventeenth-century date, though thought more probably to date to the AD 1740s conversion to a paper mill. It is this third phase that is the subject of this programme of sampling and analysis. The timber-framed building contains seven trusses, identified as A G from south-east to north-west. A plan of the building is provided in Figure 3. Inspection of the relevant timbers for dendrochronological sampling indicated the possibility that the timber framed building itself might be of two phases, or at least possibly contain timbers from two different sources. Shoesmith (The surviving Remains - Period 2) suggests that frame D is weathered on the south side indicating that the charging room floor was open to the elements when frames D - F were in place. Trusses A, B, and C are identical, having principal rafters carrying triple purlins. Each truss has a tiebeam carrying queen posts that rise to the collar. From tie beams and collars diagonal braces rise to the principal rafters. The timbers of these trusses are squarely cut, clean, and well jointed. The surface grain and the few places where cross sections could be seen suggested that the timbers of these trusses had relatively few growth-rings. Trusses D, E, F, and G may originally have been of a similar form as trusses A, B, and C, only the queen posts appear to have been removed. However, these trusses contain a number of redundant mortice and peg-holes, suggesting that they had a former use. Furthermore, unlike the neatly trimmed timbers of the first three trusses, these timbers are somewhat rougher in appearance, less squarely cut, and contain a great many more growth-rings. Drawings of the trusses are shown in Figures 4a g, taken from City of Hereford Archaeology Committee report. The possibility of the timber building having two phases was discussed with the English Heritage south-west regional office. On the basis of this discussion the scheduled monument consent allowance of fifteen samples was split between the two sections of timbering. Ten core samples, GNM-AOl - 10, were obtained from timbers of trusses D - G (those timbers with sufficient rings to most likely produce a date) and five core samples, GNM.-All IS from what appeared to be the best beams of trusses A C, whose timbers had fewer rings and were less suitable for dendrochronological analysis. The positions of the cores was recorded at the time of sampling and are shown in Figures 4a - g. Details of the samples are given in Table 1. Analvsis Each of the fifteen samples was prepared by sanding and polishing, and the growth-ring widths measured; the data of these measurements are given at the end of the report. The growth-ring widths of all the samples were compared with each other by the LittonlZainodin grouping procedure (see appendix). At a minimum t-value of 4.5 nine samples, all from trusses D - G, cross-matched with each other at relative positions as shown in the bar diagram Figure S. The growth-ring widths of these nine samples were combined at these relative off-set positions to form GNMASQOl, a site chronology of 244 rings. Site chronology GNMASQ01 was compared with a series of relevant reference chronologies giving it first ring date of AD 1438 and a last measured ring date of AD 1681.