REPORT OF PROGRESS IN SPECTRUM WORK 523 



ACCORDING TO INTENSITY. ACCORDING TO NUMBER. 



Rhodium. Glucinum (2). 



Silver. Germanium. 



Tin. Tin. 



Lead. Lead (1). 



Erbium. Potassium (1). 

 Potassium. 



DOUBTFUL ELEMENTS. 



Iridium. Ruthenium. Tungsten. 



Osmium. Tantalum. Uranium. 



Platinum. Thorium. 



NOT IN SOLAR SPECTRUM. 



Antimony. Caesium. Rubidium. 



Arsenic. Gold. Selenium. 



Bismuth. Indium. Sulphur. 



Boron. Mercury. Thallium. 



Nitrogen (vacuum tube). Phosphorus. Praeseodymium. 



SUBSTANCES NOT YET TRIED. 



Bromine. Oxygen. Holmium. 



Chlorine. Tellurium. Thulium. 



Iodine. Gallium. Terbium, etc. 

 Fluorine. 



These tables are to be accepted as preliminary only, especially the 

 order in the first portion. However, being made with such a powerful 

 instrument, and with such care in the determination of impurities, they 

 must still have a weight superior to most others published. 



The substances under the head of "Not in Solar Spectrum" are 

 often placed there because the elements have few strong lines or none 

 at all in the limit of the solar spectrum when the arc spectrum, which 

 I have used, is employed. Thus boron has only two strong lines at 2497. 

 Again, the lines of bismuth are all compound and so too diffuse to ap- 

 pear in the solar spectrum. Indeed, some good reason generally ap- 

 pears for their absence from the solar spectrum. Of course, this is 

 little evidence of their absence from the sun itself. 



Indeed, were the whole earth heated to the temperature of the sun, 

 its spectrum would probably resemble that of the sun very closely. 



