NON‐DESTRUCTIVE PORTABLE GAMMA RAY SPECTROMETRY USED IN PROVENANCING ROMAN GRANITOID COLUMNS FROM LEPTIS MAGNA,NORTH AFRICA*

Portable gamma ray spectrometry (PGRS) provides a non destructive means to analyst quantitatively large artefacts, such as building stones, for the radioelements K. U and Th. Nine Raman granitoid columns at the Leptis Magna Ruins in Windsor Great Park, London, were measured in situ by PGRS. Corrections for the environmental background contribution to the gamma ray flux measured, and for the shape and size of the columns, are described Comparison of the PGRS data with a radioelement data base for Roman granite sources indicates that most of the columns originated in the Troad area of Turkey. Two columns could not be unambiguously provenanced using PGRS alone because there is insufficient difference between radioelement concentrations in certain sources. However, non‐destructive measurements of magnetic susceptibility, used in conjunction with PGRS data, suggest that these two columns originated in the Kozak Daǧ, also in Turkey.     

MECHANICAL PROPERTIES OF STONE ARTEFACT MATERIALS AND THE EFFECT OF HEAT TREATMENT*

Mechanical testing of lithologies used for stone tool manufacture has shown that fracture toughness is the most objective measure of the quality of raw materials shaped by either flaking or pecking/grinding. Materials amenable to pressure flaking and blade manufacture have low values of fracture toughness, whereas those shaped by pecking/grinding have high values. The fracture toughness test is also the most definitive for quantifying the improvement in flaking properties of materials subjected to intentional heat treatment. Cryptocrystalline and macrocrystalline siliceous lithologies demonstrate a well-defined, gradual reduction in fracture toughness with increased temperature. When heated to optimum temperatures, their fracture toughness approaches that of obsidian, the lithology generally regarded as having the best flaking properties.     

MAGNETIC SUSCEPTIBILITY THICKNESS CORRECTIONS FOR SMALL ARTEFACTS AND COMMENTS ON THE EFFECTS OF‘BACKGROUND’MATERIALS*

Correction factors for magnetic susceptibility measurements on thin (<c. 50 mm thick > artefacts have been determined experimentally for a KT‐5 Exploranium G S. instrument using prepared blocks of Whin Sill dolerite. The cor rection factor is large (> 1.4) for samples less than 10mm thick, and reduces to 1 01 for samples of 50mm thickness. Measurements on thin samples can also be affected by the backing or substrate material on which they are measured. ‘Background’material, for example, soil or plaster, can contribute significantly to recorded measurements on artefacts, particularly for thin artefacts with low susceptibilities     

EARLY BRONZE AGE METAL TRADE IN THE EASTERN MEDITERRANEAN. NEW COMPOSITIONAL AND LEAD ISOTOPE EVIDENCE FROM CYPRUS

Summary.   This paper presents the results of chemical and lead isotope analyses of 17 Early and Middle Bronze Age artefacts from Cyprus. These suggest that a number of objects are of non-Cypriot copper and lead to the identification of several as imports, a new explanation for some artefact types as ingots and a discussion of the nature of deposits at the key Cypriot site of Vasilia. This in turn allows a reconsideration of the role of Cyprus in an Aegean/eastern Mediterranean metals trade in the early years of the second half of the third millennium BC and of the development of metalworking on the island.     

PRESELI DOLERITE BLUESTONES: AXE-HEADS, STONEHENGE MONOLITHS, AND OUTCROP SOURCES

Summary.   Chemical compositions and magnetic susceptibility data were compared for 12 dolerite bluestone implements including axes, axe-hammers and battle-axes, 11 Stonehenge monoliths (chemical data only), and potential source outcrops in Preseli, South Wales. Most of the studied artefacts are of spotted dolerite, a small number being unspotted dolerite. Bivariate graphs, discriminant analysis and t-tests were used singly and in combination to show, respectively, that the implements found at sites in England are mainly similar to Stonehenge monoliths, while the implements found in Wales have a variety of compositions and are much less similar to Stonehenge monoliths. The dichotomy between English and Welsh dolerite bluestone implements could be explained by exploitation of different Preseli outcrops or erratic assemblages derived from them. A small number of spotted dolerite implements have previously been shown to have chemical compositions atypical of and marginal to Preseli, suggesting the possibility of a source of spotted dolerite outside Preseli. Previously published analytical data in combination with the new implement/outcrop comparisons presented in this paper support derivation of the majority of analysed Stonehenge monoliths at one particular outcrop within the group of four identified by Thorpe et al. 15 years ago. Analysis of all the extant bluestone monoliths at Stonehenge (now possible using non-destructive methods) would allow progress in identifying monolith outcrop sources, and in understanding the links with the bluestone axe trade.     

THE RELATIONSHIP BETWEEN LITHOLOGY,FLAKING PROPERTIES AND ARTEFACT MANUFACTURE FOR AUSTRALIAN SILCRETES*

Mechanical properties of Australian silcrete strongly influenced raw material selection and artefact manufacture. Microcrystalline silcrete, with high compressive and tensile strength, is suitable for blade tools requiring fine retouch. Fine‐grained silcrete (high compressive strength but lower tensile strength) was often used for blade‐based implements, but is more susceptible to edge fracturing. Medium‐grained silcrete has poor flaking properties (low compressive and tensile strength) and was often used for flake manufacture. Thus material determinism can explain much of the variability in silcrete artefact morphology and assemblage composition. Silcrete compressive strength is positively correlated with percentage of microcrystalline matrix and negatively correlated with average grain size, so hand lens examination of a silcrete sample can give a good indication of its likely flaking quality.     

A Provincial Minister in Politics: Henry W. Crosskey*

Henry W. Crosskey (1826–93), a late Victorian unitarian minister who served in Derby, Glasgow and Birmingham, is now best remembered for his involvement in Liberal politics and policy, especially education, as both an advocate and as a member of the Birmingham School Board. An eloquent preacher, he was also an important geologist, recognized both for his original research and for popularising the science and its impact on theology, and a revealing figure in the evolution of English unitarian thought. From his student days at Manchester College, Crosskey was a follower of his teacher, James Martineau, but, unlike Martineau, he advocated an active role for government, particularly local government, in promoting social well‐being. In the political crises of 1885–6, though differing from Gladstone on religious education, disestablishment, and home rule for Ireland, he was unable to follow Joseph Chamberlain, a member of his congregation, into alliance with the Conservative Party. His scientific convictions led to his emergence in later life as an admirer of the broad piety of the early unitarian theologian and scientist, Joseph Priestley, whose followers had warred with Martineau's disciples in the bitter mid century struggle between ‘Old’ and ‘New’ unitarianism, thus serving as a bridge between the two schools of interpretation. He is also an important reminder of the expanding demands, internal and external, of an urban pastorate in the later 19th century.