the 6-inch and 1:2500 Ordnance Survey maps of East Lothian. After that year the East Lothian maps were drawn according to the meridian of The Buck in Aberdeenshire. Geology Traprain Law, together with nearby Berwick Law and Bass Rock, is an example of the unusual rock type Phonolite. It was intruded around 350 million years ago as a laccolith into sandstones, siltstones and dolomitic limestones of the Ballagan Formation of the Carboniferous period. During quarrying, large xenoliths of sandstone and shale have been found and recorded in detail. Detailed optical and chemical analysis have revealed the presence of small quantities of Sodalite, Olivine and Apatite. See also King Lot White Castle, East Lothian Chesters Hill Fort List of places in East Lothian hill fort References Ian Armit, Scotland's Hidden History Tempus (in association with Historic Scotland) 1998, R.W. Feachem, "The Fortifications on Traprain Law," Proceedings of the Society of Antiquaries of Scotland, 89 (1955-6), 284-9. Richard Feachem, Guide to Prehistoric Scotland London: Batsford, 1977 Stuart Piggott, Scotland Before History Edinburgh: University Press, 1982 Photo gallery Further reading Weitzmann, Kurt, ed., Age of spirituality: late antique and early Christian art, third to seventh century, no. 389, 1979, Metropolitan Museum of Art, New York, External links "Great Sites: Trapain Law", Ian Armit, British Archaeology, February 2001 Traprain Law Treasure; Scotland's Early Silver exhibition at National Museum of Scotland on Google Arts & Culture Archaeological sites in East Lothian Hill forts in Scotland Sites of Special Scientific Interest in Mid and East Lothian Former populated places in Scotland Iron Age sites in Scotland Scheduled monuments in Scotland Treasure troves of late antiquity Ancient Roman jewellery Ancient Roman metalwork