Analysis of timber and coating material on an iron anchor recovered off Aguada Bay, Goa

摘要

Distinct developments have been observed in the evolution of stone and iron anchors. A wide variety of stone anchors have been reported from Indian waters, preceding the introduction of iron anchors by the Europeans. Recently, an Admiralty Long Shanked iron anchor measuring 3.30 m long with a 4.37 m wooden stock was recovered off Aguada Bay, Goa at a water depth of 11 m. The anchor has been tentatively dated contemporary with the maritime history of Goa and Portugal between the 16th and 17th centuries. A thin and uniform coat of finely ground material has been noticed on the surface of the anchor and wooden stock, applied for the endurance of the anchor and the stock in tropical waters. The upper portion of the wooden stock was slightly weathered by the wood-borers and a deposit of bivalves and growth of barnacles were also noticed on the flukes of the anchor. The anatomical analysis of timber revealed that Terminalia spp. and Phoebe spp. timber were used for making the stock. Wood, other than teak, such as Terminalia and Phoebe were also used during the 16th and 17th centuries for anchor stocks because of their weight and endurance.This study is focused mainly on the anatomical analysis of timber to understand the timber species used in making the wooden stock of the anchor and its probable provenance. In addition, a Scanning Electron Microscope and an Energy Dispersive Spectrum analysis of the thin coat on the iron anchor as well of the wooden stock was done to infer the chemical composition of the fine powdered material applied.