SECTIONAL TRANSACTIONS. 
SECTION A.—MATHEMATICAL AND PHYSICAL 
SCIENCE. 
(For references to the publication elsewhere of communications entered in the 
following list of transactions, see page 388.) 
Thursday, August 27. 
1. Prof. L. 8. Ornstern.—Light Quantum Theory of Dispersion. 
If we want to discuss the equilibrium of electrons and radiation from the point 
of view of light quantum hypothesis, it is necessary to put the probability of collision 
of an electron and a light quantum proportional to the square of its ‘ wave length.’ 
This result leads us to the hypothesis that a light quantum is a spherical volume of 
electro-magnetic energy with dimensions of the order of wave length. This hypothesis 
may be used in order to find the refractive order. If a light quantum strikes over an 
atom a force will be exercised on the quantum which is proportional to the volume of 
the atom and to the gradient of the field in the quantum. The order of magnitude of 
this gradient may be estimated from the hypothesis mentioned. During the interaction 
the momentum of the quantum is put proportional to _ (A Planck constant, ¢ 
velocity of light in ether, v velocity in the quantum and wave length). From the above 
the retardation of a quantum by an atom can be calculated ; and taking into account 
the probability of collision with the atoms the ordinary formula for the refractive 
index for long waves can be obtained. On the same base the Rayleigh formula for the 
scattering of light can be found. 
In the light quantum theory, dispersion can be obtained by taking into account— 
just as in the old theory—the inertia of the electric masses in the atom. The influence 
of damping by radiation, which plays a part in the old theory, also finds its counter- 
part in our light quantum considerations. 
2. Miss Cucitra Pavne.—The Balmer Absorption Series in Stellar 
Spectra. 
3. Prof. H. Barreman.—The Force on a Spinning Electron. 
4, Prof. R. W. Woov.—Optical Excitation of Mercury Vapour. 
5. Prof. J. PRoupman, F.R.S.—The Effects of Capes, Bays and Islands 
on Local Tides. 
6. Dr. A. T. Doopson.—Tide-predicting Machines. 
7. Dr. B. Dasannacuarya.—The Free Path of Excitation to Emission 
of Light, |, of a Moving Atom of Hydrogen, and the Free Path of 
its Disturbance. (For abstract see Appendix, page 394.) 
