NEW YORK 



D. Van Nostrand Company, Inc., 250 Fourth Avenue, New York 3 



TORONTO 



D. Van Nostrand Company (Canada), Ltd., 25 Hollinger Road, Toronto 



LONDON 



Macmillan & Company, Ltd., St. Martin's Street, London, W.C. 2 



Copyright, 1947, 1955 



By 



D. VAN NOSTRAND COMPANY, Inc. 



Published simultaneously in Canada by 

 D. VAN NOSTRAND COMPANY (Canada), LTD. 



All Rights Reserved 



This book, or any parts thereof, may not 



be reproduced in any form without 



written permission from the author 



and the publishers. 



Library of Congress Catalog Card No. 55-6498 



First Edition, September 1947 



Four Reprintings 



Second Edition, March 1955 



PRINTED IN THE UNITED STATES OF AMERICA 

 BY LANCASTER PRESS, INC., LANCASTER, PA. 



