MOUNT WILSON OBSERVATORY. 257 



been identified. Numerous air-lines appeared in the infra-red, includ- 

 ing the well-known oxygen triplet X 7771-4. 



Mr. Merrill has also studied the air-hnes given by metallic sparks in 

 the red and infra-red; 57 air-lines between X 5927 and X 8719 have been 

 measured, of which 47 do not appear in previous Usts. Lines of nitro- 

 gen, oxygen, hydrogen, and argon are present, those of oxygen in- 

 cluding the important solar triplet at X 7771-4, which is much enhanced 

 in the spark and probably weakened in sun-spots as compared with the 

 solar disk. 34 of the 57 lines remain unidentified, and further obser- 

 vations for this purpose are planned. 



PRODUCTION OF METALLIC SPECTRA IN HIGH VACUA. 



This work has been carried on jointly by Miss Carter and Mr. King, 

 in continuation of the experiments conducted last year. The metal is 

 vaporized at the focus of a beam of cathode rays in a high vacuum and 

 the spectrum of the vapor in the path of the rays is photographed. 

 Observations of the spectra of manganese, titanium, iron, magnesium, 

 calcium, and cadmium have yielded extensive lists of lines for each, 

 the relative intensities being quite different from those of other sources. 

 Leading features are the intensification of certain line series and the 

 production of enhanced lines to different degrees with different ele- 

 ments. Little change appeared, whether the target of the cathode 

 rays was used as anode or insulated. This fact, and some resem- 

 blances to the spectrum near metallic cathodes, indicate that the con- 

 centration of the cathode stream at the distant target resulted in a 

 transfer to this point of conditions which can be obtained at the cath- 

 ode itself by proper arrangements. The experiments now in progress 

 appear to confirm this. Strong spectra at both anode and cathode 

 are obtained, which differ greatly in character and promise to throw 

 much light on the causes of pole-effect phenomena, since the radia- 

 tion processes in vacuum-tubes are subject to more definite interpre- 

 tation than those taking place in the arc. 



INVESTIGATIONS OF THE STARK EFFECT. 



In September 1918, Mr. T. Takamine, of the Tokyo Imperial Uni- 

 versity, began an investigation of the Stark effect, using the apparatus 

 employed by Mr. Anderson in 1916-17. The region from X3600 to 

 X 5700 was covered for most of the ordinary metals, with field-strengths 

 occasionally as high as 60,000 volts per centimeter. The results may 

 be briefly summarized as follows: 



(1) Lines in the spectra of the following elements were found to be 

 affected by an electric field: Ag, Au, Co, Cu, Fe, Mg, Mo, Na, N, 

 and O. 



(2) Close relations were found between the pole effect and the Stark 

 effect in the spectra of iron and nickel. 



