236 
PHYSICS: R. A. MILLIKAN 
This value should involve an uncertainty of but 1 part in 600. It will 
be seen to agree within 1 part in 500 with the value obtained directly 
from my sodium curve — a value which I estimated correct to only 1 
part in 200. 
Again the Wien constant C2 of spectral radiation is given by 
r 6.547 X 10"^' X 2.999 X 10'" , ^ , 
G = - = 1.372 X = ^-^^^^ - .0030 cm. degrees. 
The estimated uncertainty is obtained from an uncertainty of 1 part 
in 600 for h and 1 part in 1000 or k. The latest Reichsanstalt value^^ 
is C2 = 1.4300, while Coblentz^"* obtains from two different modes of 
approach C2 = 1.4322 and 1.4369. Again from Planck's equations 
C2 = (48 7rak/a)i- and o- = ac/i and the foregoing values of k and C2 
computed from e we obtain 
(7 = 5.72 X 10-12 ± 0.034 watt cm.-^ deg.-^ 
which is exactly the result recently found by Coblentz.^'^ 
A summary of the most important constants the values of which are 
fixed by the foregoing determination of e is given below with the uncer- 
tainty attaching to each. 
The Electron e = 4.774 ± 0.005 X 10-i° 
The Avogadro Constant N = 6.062 =t 0.006 X lO^^ 
Number of gas molecules per cc. at 0°C 76 cm w = 2.705 =t 0.003 X 10^^ 
Kinetic energy of translation of a molecule at 0°C £0 = 5.621 ± 0.006 X 10"" 
Change of translational molecular energy per °C e = 2 . 058 =t 0 . 002 X 10-^® 
Mass of an atom of hydrogen m = 1.662 =1= 0.002 X lO-^^ 
Planck's element of action A = 6.547 =t 0.013 X 10-^7 
Wien constant of spectral radiation C2 = 1.4312 =^ 0.0030 
Stefan-Boltzmann constant of total radiation o- = 5.72 ± 0.034 X IO-12 
Grating spacing in calcite^^ d = 3.030 =i= 0.001 A 
1 Ehrenhaft, F., Ann. Physik, Leipzig, 44, 1914, (657); 46, 1915, (261); alsoPhysik. Zs. 
Leipzig, 16, 1915, (10). 
2 Millikan, R. A., Physic. Rev., Ithaca, 32, 1911, (349-397); (Ser. 2), 2, 1913, (109-1,43). 
3 Millikan, R. A., Ihid., (Ser. 2), 7, 1916, (353-388); and Webster, D. B., (607). 
4 Millikan, R. A., Ihid., (Ser. 2), 2, 1913, (109-143). 
6 Harrington, E. L., Ihid., (Ser. 2), December, 1916. 
6 Millikan, R. A., Ann. Physik., Leipzig, 41, 1913, (759). 
7 Millikan, R. A., Physic. Rev., Ithaca, December, 1916. 
8 Millikan, R. A., Ihid., (Ser. 2), 7, 1916, (374). 
9 Bohr, N., Phil. Mag., London, 26, 1913, (1). 
10 Webster, Physic. Rev., Ithaca, (Ser. 2), 1916, (599). 
" Duane, and Hunt, Ihid., 6, 1915, (166). 
12 Millikan, R. A., Ihid., 2, 1913, (142). 
13 Mueller, Warburg, et al., Ann. Physik., Leipzig, 48, 1915, (430). 
" Coblentz, Physic. Rev., Ithaca, (Ser. 2), 7, 1916, (694). 
« Webster, D. B., Ihid., 7, 1916, (607). 
