46 

 KEPOET OF PROGRESS IN SPECTKUM WORK 



[Johns Hopkins University Circulars, No. 85, pp. 41, 42, 1891 ; American Journal of 

 Science [3], XLI, 243, 244, 1891 ; The Chemical News, LXIII, 133, 1891] 



During the past year or two a great deal of work has been done in 

 the photography of the spectra of elements and the identification of the 

 lines in the solar spectrum, which it will take a long time to work up, 

 ready for publication. Hence, I have thought that a short account of 

 what has been done up to the present time might be of interest to work- 

 ers in the subject. In the prosecution of the work financial assistance 

 has been received from the Rumford Fund of the American Academy of 

 Arts and Sciences, as well as from the fund given by Miss Bruce to the 

 Harvard Astronomical Observatory for the promotion of research in 

 astronomical physics, and the advanced state of the work is due to such 

 assistance. 



The work may be summed up under the following heads : 



1st. The spectra of all known elements, with the exception of a few 

 gaseous ones, or those too rare to be yet obtained, have been photo- 

 graphed in connection with the solar spectrum, from the extreme ultra 

 violet down to the D line, and eye observations have been made on many 

 to the limit of the solar spectrum. 



2d. A measuring engine has been constructed with a screw to fit the 

 above photographs, which, being taken with the concave grating, are all 

 normal spectra and to the same scale. This engine measures wave- 

 1-engtlis direct, so that no multiplication is necessary, but only a slight 

 correction to get figures correct to y^g- of a division of Angstrom. 



3d. A table of standard wave-lengths of the impurities in the car- 

 bons, extending to wave-length 2000, has been constructed to measure 

 wave-lengths beyond the limits of the solar spectrum. 



4th. Maps of the spectra of some of the elements have been drawn 

 on a large scale ready for publication. 



5th. The greater part of the lines in the map of the solar spectrum 

 have been identified and the substance producing them noted. 



6th. The following rough table of the solar elements has been con- 

 structed entirely according to my own observations, although, of course, 

 most of them have been given by others. 



