930 
) n—l 
vac. Oe nn 
( ) np—! 
a ——— | 
a 0.64403 0.99374 + 0.000014 | 
b 0.54623 1 | 
C 0.50873 1.00339 + 0.000006 | 
d 0.47234 1.00742 + 0.000007 | 
e 0.43597 1.01259 + 0.000010 
if 0.40478 1.01813 + 0.000013 
In the next table these results are compared with values obtained 
either by graphical interpolation or by calculation from interpolation 
formulae from the observations of PeRREAU '), RentscHLER?), Kocn *), 
SruckERT *), and GRUSCHKE *). Mascarr’s *) results, which show irregu- 
larities which were not confirmed by subsequent observers, are not 
included. 
d ‚ Perreau Rentschler, Koch ‚ Stuckert | Gruschke Siertsema 
| | | | | 
0.644 0.9936 | 0.9938 0.9917 | 0.9929 | 0.9937 | 
| | 
0.546 | 1 we ie 1 ad 1 
0.509 1.0033 1.0020 1.0031  1.0051 | 1.0083 1.0034 
0.472 | 1.0072 | 1.0053 | 1.0071 | 1.0110 | 1.0082 | 1.0074 
0.430 | 1.0096 1.0127 | 1.0173 1.0126 
| 
0.405 1.0154 | 1.0181 — 
| | 
The agreement with Perreau and Kocn is good, and with GruscuKE’ 
not quite so good. ReNrscnLer’s results deviate considerably, just as 
with air, and so too do STUCKERT's. 
The interpolation formula calculated as before becomes 
ied 8 0,0067868  0,00000614 
c= 229977814 Ae ae ee eee 
np—l ha 2 
) F. Perreau. Ann. de Ch. et de Ph. (7) 7 p. 345 (1896). 
) H. C. Rentscuuer. Astrophys. J. 28 p. 357 (1908). 
) J. Kocu. Nova acta reg. soc. scient. Upsaliensis (4) 2 No. 5, p. 46 (1909). 
') L. Sruckert. Zeitschr. f. Elektrochemie 16 p. 67 (1910). 
) G. GRUSCHKE. Ann. d. Ph. (4) 34 p. 310 (1911). 
) E. Mascart. Ann. de l’éc. norm. (2) 6 p. 61 (1877). 
