332 2 Tie Philippine Journal of Science 1921 
known are ether waves (infra-red and all shorter waves), elec- 
tronic vibrations, and atomic vibrations. The questions of 
whether a vibrating system emits or absorbs energy in quanta 
and, if so, by what mechanism, have remained for twenty years 
without a definite answer, but the value of Planck’s equation 
as representing some connection between frequency and the 
transfer of energy has become established by its signal 
success in the varied fields of radiation laws, specific heats, 
spectral series, ionization potentials, and atomic structure. 
We have, then, an empirical equation which is at present mys- 
terious, but presumably has an intelligible physical basis in one 
of three entities, or in some relation between these: the ether, 
the electron, or the positive unit. These three are so intimately 
connected in nature that no one has been able so far to point 
out just where the discontinuity lies. 
Theories have been advanced that a wave front of light (or 
other ether wave) is discontinuous, and only follows the clas- 
sical equations approximately . 19 It is generally admitted, how- 
ever, that there is no incompatibility between Planck’s equation 
and the classical theory of the propagation of waves in free 
ether. 
J'eans , 20 after a mathematical analysis of the situation, says 
that “we are called upon to revolutionize views which have long 
been regarded as well-established on the nature or meaning of 
electricity, ether, or radiation.” He cannot show just what 
view must be revolutionized, however. One of his assumptions 
has to do with the structure of the electron, which one may per- 
haps be excused from regarding as well-established. 
The favorite method of attempting to explain Planck’s equa- 
tion seems to be in assuming “discontinuous force laws” at 
small distances, or that “tubes of force” are definite actual 
realities instead of convenient conceptions . 21 It is impossible 
to say that any of these views is incorrect or absurd ; but better 
results, both in arithmetical calculation and physical intelli- 
gibility, seem to have been arrived at by those physicists who 
have modified the classical theory as little as possible. Among 
these Bohr 22 has achieved the most marked success in construct- 
19 Einstein, A., Ann. d. Physik. 17 (1905) 132; Thompson, J. J., Proc. 
Camb. Phil. Soc. 14 (1906-8) 417. 
20 Jeans, J. H., Phil. Mag. 27 (1914) 22. 
21 Thompson, J. J., Phil. Mag. 30 (1917); 37 (1919) 419; 39 (1920) 
679-90; Langmuir, I., Joum. Am. Chem. Soc. 41 (1919) 932, and many 
others. 
22 Bohr, N., Phil. Mag. 26 (1913) 1, 476, 857. 
