The mean values are: 
ha he ha ke ky 
hy, hy ky ky ky, 
O.Stets 1,07698 1,16417 1,26725 1,37188 
eens By + (0:6 = es zeta! he al 
Hence we get for the dispersion constants 
| don! 
| __(wac.) ml 
EE ee nn 
a | 0.64403 0.99446 + 0.000020 
b 0.54623 | 1 
| | 
c | 0.50873 | 1.00304 + 0.000006 
d 0.47234 1.00669 + 0.000009 
e | 0.43597 | 1.01145 + 0.000010 
f | 0.40478 1.01662 + 0.000023 
In order to be able to compare these with the results obtained 
by other observers, dispersion constants for the wave-lengths I used 
have been obtained from the results given by Mascarr '), Kayser 
and Runer*), Perreau*), SCHERL*), HERMANN *), RENTSCHLER °), Lorta‘), 
Koen *), CUrHBERTSON *), and GRUSCHKE **), either by graphical inter- 
polation or by calculation from dispersion formulae given by them; 
these results are collected in the following Table. 
Correspondence between the present results and those given by 
Perreau and by Koen is quite good both with hydrogen and with 
air. Only at 42= 0,644 does Kocn find a greater dispersion for both 
gases. For air, the agreement with Hermann and with CUTHBERTSON is 
also very good. 
1) E. Mascarr. Ann. de l’éc. norm. (2) 6 p. 60 (1877). 
2) H. Kayser and J. Runes. Ann. d. Physik 50 p. 312 (1893). 
3) . Perreau. Ann. d. Ch. et de Ph. (7) 7 p. 325 (1896). 
4) K. Scaeet. Verh. d. D. phys. Ges. 9 p. 27 (1907). 
5) K. Hermann. Verh. d. D. phys. Ges. 10 p. 477 (1908). 
6) H. C. Rentscuier. Astrophys. J. 28 p. 357 (1908). 
7) S. Lora Ann. d. Physik. (4) 29 p. 619 (1909). 
8) J. Kocu. Nova acta reg. soc. Scient. Upsaliensis (4) 2 N’. 5. p. 40 (1909). 
9) G. and M. Curugerrson. Proc. B. 5. (A) 83 p. 155 (1909/10). 
”) G. Gruscuke. Ann, d. Physik, (4) 34 p. 807 (1911). 
