A.— MATHEMATICAL AND PHYSICAL SCIENCES. 



20 



The above rules have by no means been proved for all elements, but 

 they are true for all spectra which have been disentangled up to the 

 present time, and may safely be adopted as a starting-point in the analysis 

 of further spectra. They have been almost completely verified for the 

 elements of the two short periods Li (3) to CI (17), but may be more 

 effectively illustrated by the arc spectra of the elements K (19) to Ni (28) 

 by the use of data collected by Catalan,'"' which are given in Table IV. 



The table includes references to the ' ground term ' {i.e. the highest 

 term or deepest energy level), and indicates also the regular or inverted 

 character of the terms. 



Table IV. 

 Term Systems in Aec Spectka., K-Ni. 



For the elements Rb-Pd, similar data collected by Meggers and Kiess^* 

 are given in Table V. 



Table V. 

 Term Systems in Arc Spectra, Rb-Pd. 



Note. — The numbers in brackets have been filled in from considerations of 

 symmetry. 



" An. Soc. Esp. Fis. y Quimica. vol. 23, p. 403 (1925). 

 22 Jour. Opt. Soc. Amer., vol. 12, p. 446 (1926). 



