270 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, No. 13 
modification of certain theories relating to crustal movements which 
were advanced before the theory of isostasy had been quantitatively 
studied. 
SPECTROSCOPY.—Regularities in the are spectrum of titanium. 
C. C. Kass and Harrimt K. Kruss, Bureau of Standards. (Com- 
municated by Dr. W. F. Mreacers.) 
Until recently our knowledge of the series regularities occurring in 
spectra extended only to the elements hydrogen and helium, those of 
the first three columns of the periodic classification, and also the ele- 
ments oxygen, sulphur and selenium of the sixth column. The more 
complex spectra of the elements occupying columns IV to VIII have 
for the most part remained unresolved.. The extension of our knowl- 
edge of spectra into hitherto unexplored regions, the successful 
“explanation of known spectrum regularities on the basis of modern 
atomic theories, and the recent discovery of new types of regularities 
in complex spectra have all inspired new attacks on the more complex 
spectra with successful results for chromium? and molybdenum: of col- 
umn VI, for manganese’, of column VII, and for iron’ of column VIII. 
The element titanium, of atomic number 22, is a member of column 
IV of the periodic classification. Its are spectrum is of importance in 
astrophysics, the titanium lines occurring in all classes of stellar spectra 
from Type A to Type M of the Harvard Classification. In the spec- 
trum of the sun practically all the more intense arc lines of titanium 
were identified by Rowland from wave length 3000 A up to approxi- 
mately 6900 A, and by Meggers’ from wave length 6900 A to 9000 
A. According to Adams$, 91 per cent of all the titanium lines lying 
between 4000 A and 7000 A are strengthened in sun-spot spectra. 
The are spectrum of titanium has been measured from wave-length 
2400 A in the ultra-violet to 9700 A in the infra-red. In Kayser’s 
Handbuch, vol. 6, is given a summary of all the wave-length data pub- 
1 Published by permission of the Director, Bureau of Standards. Received June 17, 
1923. 
2 Ann. der Physik, IV, 69: 147. 1922; Science, 56: 666. 1922; Anales Espai. de Fis. y. 
Quim., 21: 84. 1923. 
3B. 8. Sci. Papers, In press. 
4 Proc. Roy. Soc. London A 223: 146. 1922. 
5 Journ. Wash. Acad. Sci. 13: 243, 1923. 
® Prelim. Table Solar Spectrum, Chicago, 1896. 
7 Publ. Allegheny Observ., 6: 13. 1919. 
8 Astroph. Journ. 30: 86. 1909. 
