PREFACE. 



Calls for new editions are always gratifying- to an 

 author. It is in response to such a call that this, the 

 fourth edition of the Agassiz Association, has been pre- 

 pared. It has been carefully revised and brought up to 

 date, and is now issued with renewed acknowledgments 

 to all who have assisted in its preparation. 



H. II. BALLARD, 



Pittsfleld, Mass., Aug. 1, 1897. 



