Viii PREFACE 



During the preparation of this book I have received much assistance 

 and advice from friends and colleagues. I am grateful to the following for 

 reading certain chapters and for critical comments: Dr. W. R. G. Atkins, 

 D. F. S. Russell, Professor C. M. Yonge, Dr. J. D. Robertson, Dr. D. 

 Davenport, Dr. G. Y. Kennedy, Dr. H. W. Harvey, Mr. F. A. J. Arm- 

 strong and Dr. R. D. Keynes. Their criticisms and suggestions have done 

 much to give the book any merit it deserves, but for the errors and egregi- 

 ous blunders which remain I reserve for myself full credit. Finally, I wish 

 to acknowledge the great debt I owe to my wife for her encouragement 

 and for assistance in preparing the text. She is also responsible for prepar- 

 ing many of the illustrations, which have been redrawn from the original 

 sources. 



J. A. Colin Nicol 

 Plymouth, 1956 



