ADVERTISEMENT. 



With the rapid accumulation of scientific memoirs and discussions, 

 published from year to year in numerous journals and society proceed- 

 ings, a constantly larger expenditure of time and labor is required by 

 both the investigator and the student, to learn the sources of informa- 

 tion and the condition of discovery in any given field. Hence is felt 

 the growing need of classified indexes to the work done in the various 

 fields of research, and hence the corresponding tendency of the age to 

 supply such demand. 



The present work aims at a general survey of Spectroscopic Literature, 

 with references to authorities in its more special subdivisions, and it has been 

 prepared for the Institution by Mr. Tuckerman, without other remuner- 

 ation than the expectation of serving the interests of scientific inquirers. 



It has been brought down to the middle of the year 1887. 



S. P. Langley, 



Secretary Smithsonian Institution. 



Washington, February, 1888. 



(iii) 



