8 INFLUENCE OF A MAGNETIC FIELD UPON THE SPARK SPECTRA OF IRON AND TITANIUM. 



tions are but incompletely considered. The range of spectrum covered previously has not been sufficient 

 to draw any conclusions regarding the variation of separation with wave-length, the comparison with 

 pressure effects and other changes of physical condition has not been carried out, and no application 

 has been made of Runge's rule for the commensurability of the distances between components. These 

 points will be handled in the present paper as fully as the material will permit.* 



4. Former Investigations of the Zeeman Effect for Titanium. 



A set of measurements was pubHshed by Purvis (50) for many of the stronger lines of titanium from 

 X 2S00 to X 5000. The majority of these are in the ultra-violet, 86 lines being measured in the region 

 covered by my tables. Three violet triplets were measured by Reese (12). A former paper by the author (51) 

 gave descriptions and measurements for 291 lines between X3900 and X6600. These were made from 

 the first set of plates taken in this laboratory, the first and second orders of the 13-foot (4 m) spectro- 

 graph being used, with a field of 12,500 gausses. The data for the present paper were compiled from a 

 much more extensive set of plates, taken with higher dispersion and stronger field, the gain in all points 

 being so great that these measures may be taken as superseding the previous ones. A still earlier paper 

 by the author (52) gave preliminary measures of some titanium and iron lines in a discussion of the charac- 

 ter of their separation in the laboratory as compared to that observed in sun-spot spectra. 



* Note added January, 191 2: A dissertation by Immina Maria Graftdijli on Magnetische SpUlsing van h:l Nikkei- en Kobalt- 

 Spectrum en van liet Ijzer-Speclriim (Amsterdam, igii) has just been received. Measurements are given for 38 of the stronger iron 

 lines between / 4300 and > 6500 for a field of 32,040 gausses. The measured separations of triplet lines agree in general very closely 

 with those presented in this paper. The only notable discrepancies are for a few comple.x lines where a large difference in field 

 necessarily alters the appearance of the components which are measured. 



