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VI. Bakerian Lecture.— Series Lines in Spark Spectra. 
By A. Fowler, F.R.S., Assistant Professor' of Physics, Imperial College, 
South Kensington. 
MS. received April 20,—Lecture delivered April 2, 1914. 
[Plate 3.] 
Contents. 
Section. Page 
1. Introductory.226 
2. Wave-lengths of the “4481 ” series of magnesium.228 
3. Formulae for the Mg “ 4481 ” series.230 
4. The Doublet series of calcium, strontium, and barium.233 
5. The Doublet system of magnesium. 239 
6. A new system of magnesium doublets.242 
7. Eelation between the “ 4481 ” and the new series.244 
8. The Principal series of the new doublet system.245 
9. Eelation between the two systems of doublets.247 
10. Combination lines and series of magnesium.251 
11. General comparison of Mg, Ca, Sr, and Ba.254 
12. The spectra of hydrogen and helium.. .. . 254 
13. Enhanced lines in relation to Bohr’s theory.258 
14. Summary.263 
Appendix. . 264 
Description of plate.266 
List of Tables. 
I.—The “4481 ” Series of Magnesium. 
II.-—Less Befrangible components of Mg “ 4481 ” Series. 
III.—Calcium Doublets. 
IY.—Strontium Doublets. 
Y.—Magnesium Wide Doublets. 
VI —Magnesium Wide Doublets—Eevised Data. 
VII.—New (“F.P.”) Doublets of Magnesium. 
VIII.—Principal Series of “F.P.” Doublets. 
IX.—Principal Series of Wide Doublets (Preliminary Calculation). 
X.—Corrected Principal Series of Wide Doublets. 
XI.—The “F.P.” Doublet System of Magnesium (Wave-numbers and “Variable Parts”). 
XII.—Magnesium Combination Series A. 
XIII. —Magnesium Combination Series B. 
XIV. —The “ 4686 ” Series of Proto-helium. 
XV.—The “ Pickering ” Series. 
XVI.—Enhanced Lines of Magnesium. 
VOL. CCXIV.—A 514. 2 G 
Published separately, July 18, 1914. 
