Anatomical identification of a historic wooden wedge from the construction of Cais das Colunas (Lisbon, Portugal)

Abstract

The historic quay Cais das Colunas was constructed during the decades 1770-1790. In 1996 was partially dismounted and in 2008 was reconstructed. During these interventions some samples of materials were collected, in order to characterize them. It was collected a wooden wedge, of 25 centimeters long, used during the construction process of the historical quay to adjust one of the stone blocks. The (re)construction of Lisbon, after the 1755's earthquake, depended on huge quantities of wood. Recent historic survey confirmed that tons on wood came to Lisbon from various regions of Portugal (such as Alcácer do Sal and Marinha Grande) and also from some European countries – particularly from Sweden and from the Netherlands. There were already identified, in Pombaline structural elements of the buildings, species already introduced at Portuguese forestry at that time, such as Quercus pedunculata, Castanea sativa, Quercus suber and Quercus ilex; and also other non introduced species, at that time, like Larix decidua or nordic Pinus sylvestris. Species from other continents are also referred in literature: Pinus caribaea, Swietenia macrophylla and Tectona grandis. The present study focuses on the anatomical identification of the wood of the wedge, in order to identify its specie and then to try to determine the material's geographical origin - based on the available knowledge of the distribution of species in the second half of the XVIIIth century. The sample was studied according recommendations of IAWA: (1) macroscopically and (2) microscopically, through transversal, tangential and radial sections of approximately 17 to 20 μm thickness obtained with a sliding microtome, stained with Safranin and mounted on Eukitt; a dissociation process of the lignin (stained with astrablau) was also performed. A microscope Leica DML coupled with a digital camera and the image analysis system LEICA Qwin Plus software Leica, allowed the acquisition of images. The anatomical features of the sample disprove the existing premiss of a nordic P. sylvestris, from Sweden or from the Netherlands. The observed anatomy i.e. coalescence of pinoid pits to windowlike and the type of inner wall thickening of ray tracheids are described in some Pinus spp such as Pinus caribea; but extra survey has to be developed in order to know the wood specie of the wedge and determine its geographical origin.