I9I2.] PICKERING— THE OBJECTIVE PRISM. 567 



already classified twenty-seven thousand spectra. The completed 

 catalogue will fill four of the quarto volumes of the Annals of the 

 observatory, of about two hundred and fifty pages each, and will 

 give the class of spectrum of nearly all of the stars of the eighth 

 magnitude and brighter, besides many others. Some of these are 

 so faint that they are not contained in the Cape Photographic 

 Durchmustening . 



Dr. Draper thus placed in our hands a wonderful tool for ana- 

 lyzing the stellar universe. His memorial furnishes not only a 

 permanent record in print of great extent, but, through the collec- 

 tion of photographs, will permit in the future a vastly greater 

 number of facts to be derived from them. 



PROC. AMER. PHIL. SOC. , LI. 207 J, PRINTED JAN. l"] , I913. 



