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Published online by Cambridge University Press: 25 April 2022
(1) I am pleased to acknowledge the assistance of Joanna Scadden, Manager of the Royal Geographical Society Picture Library in the preparation of the lecture on which this paper is based and her kindness in making the images available for reproduction.
(2) The images used in the lecture and the accompanying display are listed in the appendix below. References to this list in the test appear in square brackets.