Copyright, 1930 



BY 



Arthur T. Henrici 

 Copyright, 1947 



BY 



John Wiley & Sons, Inc. 



All Rights Reserved 



This book or any part thereof must not 

 be reproduced in any form without 

 the written permission of the publisher. 



SECOND edition 



Second Printing, June, 1947 



PRINTED IN THE UNITED STATES OF AMERICA 



