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Published online by Cambridge University Press: 02 January 2015
The difticulties surrounding the proper excavation and display of poorly preserved skeletal remains are well known to excavators. Where the bone is moist and friable, care is required to avoid touching it until it has dried and hardened. When it is stained as well, so that there is little contrast between bone and soil, then the excavator's task can indeed be difficult. In such cases photographic presentation often shows less than was seen by the excavator since differences just perceptible to the eye are likely to fall well short of the contrast level which can be recorded satisfactorily by the camera. Those sandy soils in which the stain is well displayed are the fortunate exception. In an endeavour to overcome these difficulties ultra-violet radiation has been tried.
The light of the visible spectrum extends from a wavelength of 7,000 Å at the red end to 4,000 Å at the blue end (n. 1). The shorter wavelengths extending to 140 Å form the ultra-violet region, but most of this is lost for present purposes since ordinary optical glass absorbs all radiation below about 3,500 Å. However, phenomena which can be used are found in this band between 3,500 Å and 4,000 Å. Emissions of these wavelengths are not visible to the human eye but some substances possess the property of absorbing such radiation and in turn emitting new radiation at longer wavelengths, including those which are visible. This is the phenomenon known as fluorescence.
(1) In the case of light, wavelengths are measured in Ångstrom units (Å). One Ångstrom unit equals one ten-millionth of a millimetre.
(2) Van Ledden-Hulsebosch, C. J., Archiv für Kriminologie, 78 (1926), 6; cf. Hormann, K., Schumacher Festschrift, Mainz, 1930, 77-79, pl. 6.
(3) Radley, J. A., Photography in Crime Detection, London, 1948, fig. 70.
(4) Leroi-Gourhan, M. A., Bulletin de la Société Préhistorique Française, 49 (1952), 7; Rev. de Geog. de Lyon, 27 (1952), 425-433.
(5) Dorchester Site XII. Professor R. J. C. Atkinson.
(6) For definitions, fuller information on techniques, and bibliography, see Radley, J. A. and Grant, J., Fluorescence Analysis in Ultra-Violet Light, London, 1954. Also Summer, W., Ultra-Violet and Infra-Red Engineering, London, 1962.
(7) Elenbaas, W. et al., Fluorescent Lamps and Lighting, Eindhoven, 1959; App. 2, Hehenkamp, Th., ‘Transistor Circuits’.
(8) Skateraw, Dunbar. Discovery and Excavation: Scotland 1958, Glasgow, 1958, 39.
(9) Isbister, South Ronaldsay. Ritchie, P. R., Proceedings of the Society of Antiquaries of Scotland, 92 (1958-59), 25-32.
(10) Cf. Nickolls, L. C. The Scientific Investigation of Crime, London, 1956, 10-11. Details from Atlas Lighting Ltd., Thorn House, Upper St Martin’s Lane, London, W.C.2.
(11) This study was undertaken before exposure meters using cadmium sulphide photo-cells became generally available.
(12) Dunn, J. F., Exposure Meters, London, 1958, 174.
(13) We are indebted to the Royal Commission on Ancient and Historical Monuments for Scotland for the loan of the necessary equipment.
(14) Luckiesh, M. and Taylor, A. H., General Electric Review, 42 (1939), 274. For general discussion of this topic see Luckiesh, M., in Knowlton, A. E., Standard Handbook for Electrical Engineers, London, 1957, 2186-2190.
