XII. On the Scattering and Absorption of Light in Gaseous Media^ with 
Applications to the Intensity of Sky Radiation. 
By Louis Vessot King, B.A. {Cantab.), late Scholar of Christ's College, Cambridge; 
Lecturer in Physics, Mctxill University, Montreal. 
Communicated by Sir Joseph Larmoe, Sec. R.S. 
Received June 7,—Read November 7, 1912. 
Contents. 
Part I. Page 
General theory. 375 
Part II. 
Application to the Earth’s atmosphere.380 
Part III. 
Analysis of Observations on absorption and scattering. Summary. Numerical tables. Diagrams 
illustrating attenuation of sunlight and intensities of sky radiation.401 
Part I. 
§ 1. On the Scattering of Parallel Radiation by Molecules and Smcdl Particles. 
The eftect of small particles in scattering incident radiation was first worked out by 
Lord Rayleigh.* When a stream of parallel radiation falls on a particle whose 
dimensions are small compared with the wave-length the resulting secondary 
disturbance travels in all directions at the expense of the intensity in the original 
direction. In a later paper Lord Rayleigh! gave reasons for believing that the 
molecules of a gas are themselves able to scatter radiation in this way. In a gaseous 
medium it is legitimate to sum up the intensities of the scattered radiation due to 
each molecule in an element of volume without a consideration of phase-difference in 
consequence of the continuous change in the relative positions of a molecule in a gas. 
* Rayleigh, ‘Phil. Mag.,’ XLL, pp. 107, 274, 447 (1871); XII., p. 81 (1881); ‘Collected tVorks,’ 
vol. I, pp. 87, 104, 518. 
t Rayleigh, ‘Phil. Mag.,’ XLVII., pp. 375-384 (1899); ‘ Collected Works,’ vol. IV., pp. 397-405. 
YOL. CCXII.-A 495. Publislied seiarately, February 8, 1913. 
