REFERENCES blakf. c. (1971) A preliminary report on survey work of some slate tips in Caernarvonshire. Nature Conservancy. Bangor. CROMPTON. c. T. (1967) The treatment of waste slate heaps. Town Planning Review. 37, 291-304. SHELDON. J. c. (1974) The growth of amenity trees in difficult conditions. In Tree Growth in the Landscape. In Press. TUCK. c. J. (1973) Derelict Land. Merioneth Structure Plan, Subject Report No. 15. Department of Planning & Design, Land Reclamation Section, Town Hall, Sheffield. British Birds is the only monthly journal devoted to field studies of the birds of the British Isles and western Europe. Each issue contains plates by leading bird photographers. Prospectus from 61/62 Watling Street, London, EC4.