“The inner quantum number () differs from one component of a multiple term to another, and also in the various series and systems, according to the following scheme. Series Singlets Doublets Triplets Quartets Quintets Sextets Septets 1 s j = 0 1 1 2 2 3 3 2 p 1 1,2 0,1,2 1,2,3 1,2,3 2,3,4 2,3,4 3 d 2 2,3 1,2,3 1,2,3,4 0,1,2,3,4 1,2,3,4,5 1,2,3,4,5 4 f 3 3,4 2,3,4 2,3,4,5 1,2,3,4,5 1,2,3,4,5,6 0,1,2,3,4,5,6 5 g 4 4,5 3,4,5 3,4,5,6 2,3,4,5,6 2,3,4,5,6,7 1,2,3,4,5,6,7 “Combinations occur only between terms for which differs by 0 or ± 1. If, however, in both cases, no radiation occurs. Lines corresponding to a change of are found in strong magnetic fields, and a very few in their absence. “The combination of two multiple terms gives rise, therefore, to a group of lines (which may number as many as eighteen). Such groups have been called multiplets by Catalan. Their discovery has afforded the key to the many-lined spectra.... “In such a group, those lines for which the changes in and , in passing from one term to the other, are of the same sign, are the strongest, and those in which they are of opposite sign the weakest. These intensity relations are of great assistance in picking out the multiplets. “Combinations between terms of different systems (consistent with the foregoing rules) often occur. Such lines are usually, though not always, faint.... “The serial number of the term (which is equivalent to the total-quantum number) plays quite a subordinate rôle, being of importance only when series formulae have to be calculated. An extensive analysis of a spectrum is possible without it, though determination of the limits of the series, and the ionization potential, demands its introduction.” [Pg 205] III. MATERIAL USED IN CHAPTER VIII THE line intensities quoted in Chapter VIII were derived from the spectra of the stars enumerated below in Table XXXII. Successive columns contain the Draper class, the name of the star, the Boss number, the visual apparent magnitude, and the reduced proper motion H. The stars within each class are arranged in order of right ascension. TABLE XXXII Class Star Boss m H Class Star Boss m H Cen 3054 3.3 1.7 Vel 2723 4.1 5.1 Phe 148 4.5 -0.5 Sgr 4832 2.7 0.0 For 474 4.7 0.1 Gru 5880 3.7 4.1 Eri 6ll 4.5 4.3 Eri 696 4.2 5.1 Dor 1081 3.5 2.1 Pic 1446 3.9 3.7 Vel 2356 2.0 1.9 Mus 3092 3.8 3.9 Car 2493 1.8 3.2 Pav 5315 3.6 2.1 Cen 3302 2.4 3.9 PsA 5916 1.3 4.1 TrA 3879 3.1 2.2 Hyi 458 3.0 5.0 Sgr 4645 2.0 2.7 Car 1622 0.9 -4.6 [Pg 206] Car 2503 2.2 -0.7 Crv 3172 3.2 2.3 Boo 3722 3.0 4.3 Hyi 3622 5.5 4.6 Cir 3739 3.4 5.0 Cen 3623 2.3 6.7 TrA 4030 3.0 6.2 Lup 3864 3.5 4.0 Sco 4457 2.0 -2.6 Lib 3962 5.3 -1.2 Sco 4361 3.4 5.7 Apo 4168 3.9 4.6 Sgr 4874 3.0 1.0 Sco 4272 2.4 6.5 Vol 1917 4.0 0.6 Sgr 4568 3.1 4.6 CMi 2008 0.5 6.1 Sgr 4628 2.8 1.3 Pup 2153 2.9 2.9 Sgr 4665 2.9 4.4 Vel 2324 4.1 0.0 Sgr 4809 3.6 1.4 Oph 4421 4.4 5.4 Sgr 4857 3.4 5.5