222 CARNEGIE INSTITUTION OF WASHINGTON. 



tion of certain ionizing potentials and the study of many other funda- 

 mental aspects of the question will be undertaken at the California 

 Institute. 



Another problem calling for the joint activity of the Institute and 

 the Observatory is that which involves the combined effect of electric 

 and magnetic fields on radiation. The nature of this effect has been 

 sought by the writer because of his desire to decide conclusively 

 whether the existence of electric fields can be detected in sun-spots or 

 other solar phenomena, and also because of the important bearing of 

 the effect on the structure of the atom. If an electric field exists in a 

 sun-spot, the radiating particles within it must be subjected simulta- 

 neously to the influence both of the electric field and the magnetic 

 field of the spot. No evidence of the Stark effect has been detected in 

 sun-spot spectra, and the weakening of the enlianced lines and other 

 evidences of low ionization seem to indicate that a strong electric 

 field can not be present. It has nevertheless been thought advisable 

 to undertake in our laboratory an investigation of the effect of the 

 combined fields, the preliminary results of which are given in this 

 report (p. 288). In this work, done with the efficient aid of Mr. Sin- 

 clair Smith, we have fortunately had the use of the powerful coreless 

 magnet designed by Dr. Aaderson (p. 288), which gives a field of 

 33,000 gausses with a current of 4,000 amperes, and is admirably 

 adapted for the insertion of our special quartz vacuum-tubes within 

 the uniform magnetic field. This magnet is also especially adapted 

 for the study of the inverse Zeeman effect with the aid of an electric 

 furnace designed by Dr. King for this purpose (p. 286). 



Dr. King's regular investigations of furnace spectra have dealt for 

 the most part with the emission lines of manganese, scandium, cad- 

 mium, yttrium, neodymium, and zirconium, and the absorption spectra 

 of iron and the alkali metals. Between X2795 and X6605, 270 manga- 

 nese lines have been classified on the basis of their temperature varia- 

 tions between 1,560° and 2,400° C; 307 scandium lines have also been 

 classified, and the characteristics of the enhanced lines and of those 

 strengthened at low temperatures have been determined. As the en- 

 hanced lines are the only ones that are strong in the solar spectrum, it 

 is of interest to learn that these are produced in the furnace at moderate 

 temperatures, in some cases as low as 2,250° C. The low-temperature 

 lines, absent for the most part from the solar spectrum, are naturally 

 strengthened in spots. In the work on absorption spectra it has been 

 found possible at the highest temperatures (3,200° C.) to reverse prac- 

 tically all the iron lines as far as X6700. Such high temperatures have 

 also rendered it possible to photograph the subordinate series of so- 

 dium, potassium, and calcium in absorption, giving improved wave- 

 lengths and better values of the series constants. 



Dr. Anderson's work on the absorption spectra of electrically ex- 

 ploded iron wires has been continued with high dispersion over the 



