An Alternative View of Relativity. 433 



now painted with thick black paint, with the exception of 

 the dotted portion o£ the three bulbs. They are mounted in 

 a horizontal position, and sunlight, reflected from a mirror, 

 is focussed at the centre, with a 6-inch reading-glass, the 

 light entering through one o£ the lateral bulbs and passing 

 out through the other. Observations are made through the 

 clear portion of the bulb B. A nigrometerwith a hole about 

 8 mm. in diameter will be found of assistance in viewing the 

 luminosity of the gas at the focus, though in the case of ether 

 it can be seen at once even in a well-lighted room. 



Summary. 



1. The intensity of the light scattered by a given thickness of 

 dust-free air in a tube illuminated by concentrated sunlight, 

 has been compared photometrically with the light of the sky, 

 by reducing the intensity of the latter until a match was 

 secured. The ratio of the two intensities was compared with 

 the calculated ratio, making certain assumptions in the case 

 of the light of the sky, and a fair agreement found. 



2. The intensity of the light scattered by dust-free air 

 nearly in the direction of the incident light has been examined 

 and found to be not very different from the intensity scattered 

 in a perpendicular direction. It is theoretically twice as 

 bright, but the conditions of the experiment did not permit 

 of the determination of a difference of this amount. This 

 indicates that the enormous increase in the intensity of the 

 sky close to the sun's limb (over 20-fold) results from 

 diffraction by motes in the air, and would be wholly absent if 

 the atmosphere were perfectly clean. 



3. The scattering power of the air near the ground on the 

 clearest days in the country has been found to be about 

 2' 6 times the average scattering power of the atmosphere. 



XLIL An Alternative View of Relativity. 

 By Prof. Fkederick Slate, University of California *. 



MANY expositions of relativity are marred at two points 

 in the cogency of their aggressive argument for 

 rejecting Newtonian dynamics. Where their reasoning is 

 based explicitly or by implication on a statement of Newton's 

 second law for constant inertia, supported by a " Principle 

 of vis viva " requiring all work to be recorded as change of 

 kinetic energy, these two restrictions foredoom to failure the 



* Communicated by the Author. 

 Phil May. Ser. 6. Vol. 39. No. 232. April 1920. 2 F 



