This page needs to be proofread.

First Published 1925

Reprinted 1925, 1927, 1931

First Revised Edition 1958

This book is copyright under the Berne Convention Apart from any fair dealing for the purposes of private study, research, criticism or review, as permitted under the Copyright Act, 1956, no portion may be reproduced by any process without written permission Enquiry should be made to the publisher

This revised edition © George Allen & Unwin Ltd, 1958

PRINTED IN GREAT BRITAIN

in 11-pt Bell type by

UNWIN BROTHERS LIMITED WOKING AND LONDON