LONDON 



Leonard Hill [Books] Ltd. 



9 Eden Street, N.W.i 



NEW YORK 

 Interscience Publishers, Inc. 



250 Fifth Avenue, New York i 



FIRST PUBLISHED IN GREAT BRITAIN I961 



© P. H. Gregory, 1961 



DEDICATED 



to 



my wife 



Margaret Fearn Gregory 



PRINTED IN GREAT BRITAIN AT 

 THE UNIVERSITY PRESS 

 ABERDEEN 



