26 Journal of the ^Iitciiell Society [September 



A. H. Patterson — The Ether vs. What? 



The older theories of the ether were given, and the various theories 

 of light described, with the reasons for and against each. The dif- 

 ficulties attendant upon the results of experiments of Airy, Lodge, 

 Michelson and Morley, etc., were described, and the newer attempts 

 to frame theories to account for all observed facts were presented: 

 the wave theory, the ether-storing theory, the Cone-Ray theory and 

 the Quantum theory. 



Each of these was examined as to its ability or inability to ex- 

 plain Ionization and Photo-electric effects, Interference effects and 

 Quantum relations. In the course of the discussion of the paper 

 Einstein's latest views on the subject were brought out. 



253rd Meeting-^January 10, 1922 



6. M. Braune — Experimental Determination of Lateral Earth Pres- 

 sures. 



The question of finding the correct or approximately correct lateral 

 pressures existing in masses of granular material such as earth pres- 

 sures against retaining walls or grain in elevators has been studied 

 by physicists and engineers for a great many years. 



The problem as occurring most often in engineering structures 

 is the active pressure against retaining walls. The correct determi- 

 nation of this force affects the design of construction work, involving 

 the expenditure of millions of dollars yearly, and therefore a proper 

 knowledge as to its correct magnitude is of great economic value. 



C. A. Coulomb, the French physicist and engineer, was probably 

 the first one to present a working theory for the determination of 

 earth pressures. Rankin, the great English engineer, developed the 

 theory on the assumption that the filling material behind the wall 

 consisted of an incompressible homogenous granular mass of un- 

 limited extent, without cohesion, the particles being held together 

 by friction on each other. These assumptions lead to the ellipse of 

 stress and make the resultant earth pressure on a vertical surface 

 parallel to the top surface. The German engineers have also given 

 much study to this problem and some valuable experiments have 

 been made by ]\[ueller-Brpslau at the Charlottenberg Laboratories. 

 In America Major William Cain has contributed more than anyone 

 'ilse in tills country, and is considered an authority on the subject. 



