BOOK REVIEWS Geology Explained in South Wales. T. R. Owen. David & Charles, Newton Abbot. £ 3.50. This book describes the geology, scenery and the effects of geology and landforms on the lives of men in an important geological area — a classic area, indeed-after which many divisions of geological time have been named. In German or Japanese, the early geological periods are known as Pre-Cambrian, Cambrian, Ordovician, Silurian, and their divisions bear West Wales names-Llandeilo, Llandovery, Llanvirn, Caerbwdy, Caerfai. In the Moscow Geological museum, I am told, is a specimen labelled 'Haver- fordwestski Gasworkski Mudstoneski! The book is truly a vade mecum. Stop at Treffgarne Quarries on the A40, take out the book, turn to p.36, and read all about the exposed ashes, purple and green, and why they make excellent road chippings, while the harder Pre- Cambrian rhyolites (of which Maiden Castle crags) are unsuitable. At Carreg Cennen (p.66) learn how the castle is perched on a lime- stone bluff caught between two faults of the Carreg Cennen distur- bance. It is a pity the author has been lured away from his subject now and again. Mention must be made of the last invasion he says illogically and proceeds to give a garbled version of the 1797 charade. He should also have taken the trouble to spell Welsh place-names correctly. Mr. Owen is a senior lecturer in Geology at University College, Swansea. Geology Explained in North Wales by John Challinor and Denis E. B. Bates, in the same series at £ 3.25, suffers likewise from wrongly- spelt place-names. It gives a comprehensive coverage, particularly of the north-western quarter of Wales, and special attention is paid to the relationships between structure and scenery. Professor Emeritus E. G. Bowen contributes a masterly chapter on the role of geology in the service of man. Each volume has a handy glossary of geological terms and an extensive bibliography. John Challinor, formerly senior lecturer in Geology at Aberystwyth and a Trust member, has contributed to this journal, which is listed in the bibliography. Animal Migration. Tony Harrison. Hamlyn, London. 5 Op. There have been many books written of late on animal migration and navigation. None gives the answer to the mystery that has intrigued man, probably since prehistoric times. Abraham must have scratched his head as I did 4,000 years later, each time the storks wheeled over Jerusalem. Mr. Morrison adds little to the mystery or to its solution, or to our knowledge. In fact, one feels one could improve his knowledge, e.g. on the Grey Seal and the Manx Shearwater, and refer him to R. M. Lockley's book Animal Navigation, which he does not list in his