INTRODUCTORY NOTE BY W. K. BROOKS. 



As my name appears on the title-page of this Memoir as joint author, I take this opportunity to say that my 

 own share in the work has been that of instructor and director only. The investigations are the exclusive work of 

 Dr. R. P. Cowles, and while I have followed them in detail, and hold myself responsible for their soundness and 

 accuracy, the credit for the research belongs to Doctor Cowles alone. 



Dry Tortugas, Florida, July 3, 1905. 



72 



