38 Journal of the Mitchell Society [August 



mean density of matter. Dr. Henderson presented the results of 

 certain investigations carried on in the advanced seminar on General 

 Relativity which he conducted here this year, giving figures and 

 computations for the size of the universe, on the assumption that the 

 mean density of matter was the same as that of the Milky Way. For 

 example, the radius of the "spherical" space universe of Einstein 

 w^as found to be one million times one billion times the distance from 

 the earth to the sun. It was found that a ray of light travelling at 

 the rate of approximately 186,000 miles per second would go around 

 this universe in one billion years. These and other results were given 

 to convey some notion of the size of the universe worked out upon 

 the basis of Einstein's results. 



Otto Stuhlman, Jr. — Radiations Lying Between the Ultra-Violet 

 and X-Ray Spectrum. 



It was found that when thermions liberated from a tungsten fila- 

 ment were accelerated and allowed to impinge on a metal grid main- 

 tained at a variable positive potential that secondary electrons were 

 emitted from the grid. The number of such secondary electrons 

 emitted were measured by means of a galvanometer in series with the 

 grid and a plate maintained at a constant positive saturation potential. 



On plotting the secondary current as a function of the accelerating 

 voltage acting on the primary electrons, a sudden change in the slope 

 of the curves occurring at critical potentials were interpreted as V 

 (volts) xL (Aengstrums) =12320. 



The critical voltages at which emissions occurred were found to 

 be : Tungsten 4.4, 17, 35.6, 60, 135, 144, 181, 295, 435, 1750. Iron : 

 3.3, 8.5, 10.4, 24.3, 45.8, 200. 



265Tn Meeting— May 8, 1923 



Dr. Ivey F. Lewis, Exchange Professor from the University of Vir- 

 ginia (U. N. C, class of 1902) — The Age and Area Hypothesis. 

 (By invitation). 

 The hypothesis known by this name was proposed by Willis in 1907 



and has since been somewhat modified and enlarged in numerous 



papers. It is thus stated by its author : 



"The area occupied (determined by the most outlying stations) 



at any given time, in any given country, by any group of allied 



