X PREFACE 



and would have liked — but this is unavoidable. Some potential authors of 

 central importance in their fields refused an invitation to contribute to this 

 volume for lack of time or because their field had too recently been reviewed 

 elsewhere; others accepted the invitation but did not produce the papers. 

 Still other authors developed new and unexpected interests and wrote with 

 enthusiasm on topics quite different from the one they had been invited to 

 cover. When all these circumstances are considered, the coverage is better 

 than might have been predicted, especially since a surprisingly high propor- 

 tion of the authors who promised papers actually produced them. 



Grateful acknowledgment is due to the authors who contributed papers, to 

 the members of the Golden Jubilee Committee, to friends and colleagues who 

 nominated potential authors, and to many others who helped in the planning 



and the preparation of this volume. -.rr -jr- ^ , 7j c^ 



WUltam Campbell Steere 



