254 CARNEGIE INSTITUTION OF WASHINGTON. 



Miscellaneous Experiments with the Furnace. 



About 80 electric-furnace spectrograms have been made for purposes 

 not already mentioned. These included supplementary photographs 

 of the spectra of manganese, iron, and chromium; a series for the 

 cerium spectrum at various temperatures ; a series for iron, copper, and 

 silver at atmospheric pressure for comparison with vacuum spectra 

 in connection with questions as to the character of the furnace radi- 

 ation; and several photographs of barium and strontium for the 

 measurement of lines which are sharper in the vacuum furnace than 

 in other sources and important in the evaluation of series constants. 



A detailed comparison of electric-furnace material with that for 

 sun-spot spectra has been made, but is as yet incomplete, some points 

 requiring more observational data. The relation indicated in the early 

 work, namely, that low-temperature lines are strengthened and high- 

 temperature lines weakened in sun-spots has been found to be very 

 general, the more pronounced cases of strengthened spot-lines being 

 those appearing with especial strength in the furnace as compared 

 with the arc or spark. Various differences of detail were found for 

 different elements. In the spectra of titanium and vanadium, a large 

 number of lines which are fairly strong in the furnace agree closely 

 with sun-spot lines which are faint in the solar spectrum and uniden- 

 tified by Rowland. Their origin seems thus to be established, and the 

 furnace can be employed for any detailed study of such lines that 

 seems desirable. 



SECONDARY STANDARDS OF WAVE-LENGTH. 



The redetermination of secondary standards of wave-length in the 

 iron-arc spectrum by Mr. Babcock and Mr. St. John is now nearly 

 complete over the region XX 3370-6750, in so far as the interferometer 

 program is concerned. During recent months about 30 plates have 

 been taken for this purpose, covering the region XX 5400-7300; 18 of 

 these, including the best photographs, have been measured and re- 

 ductions are nearly complete. Numerous iron lines, in addition to 

 the international secondary standards, were observed, and several of 

 the plates contain spectra of barium, strontium, or calcium from a 

 vacuum arc as well as the iron standards, thus making available 

 many excellent tertiary standards at the same time. 



Because of numerous extensions into the infra-red of spectroscopic 

 work now in progress, and the present lack of secondary standards 

 beyond X G750, the program includes the establishment of reliable new 

 standards free from pole effect over the region which can profitably 

 be observed with the aid of dicyanin. It is likewise highly important 

 to determine many new standards in the ultra-violet region, as the 

 adopted list of secondary standards terminates at X 3371. As noted 

 elsewhere, the interference apparatus is being arranged for opera- 



