PREFACE ix 



constant source of encouragement. I should like to mention specifi- 

 cally Mr. F. B. Isakson and Lt. R. Gomory from the Office of Naval 

 Research, Washington, and, former members of the same office, Lt. 

 Comdr. F. L. Thomas, Lt. D. de Graaf, and Mr. L. M. McKenzie, 

 and, from the Boston office, Capt. J. F. Benson, Dr. C. F. Mucken- 

 haupt, and Mr. T. B. Dowd. 



Acknowledgment is also due to Mr. D. A. Berkowitz, Mr. R. H. 

 Davis, Mr. P. Felsenthal, Dr. W. L. Harries, and Dr. G. F. Vander- 

 schmidt, who have been working with me at different times and who 

 have given me valuable assistance, and to Mrs. E. Duncan for her 

 competent help in preparing and typing the manuscript. 



I am aware that a book of this kind is bound to be incomplete 

 and contain errors. I should appreciate any information that will 

 lead to desirable corrections in the text, and I hope that with such 

 help something of value may grow in time. 



Kurt S. Lion 



