632 Mr. L. B. 8myth on the Supply of Radium 



that increase of concentration beyond a certain point is 

 detrimental to the foaming power. 



It cannot be claimed that this simple statical theory gives 

 a complete explanation of the essentially dynamical process 

 of foaming. Nevertheless a comparison between theory and 

 experiment, even it' it simply demonstrates the insufficiency 

 of the theory, will yield valuable information as to the nature 

 of the process*. 



The University, Leeds, 

 July 11, 19] 2. 



LX. On the Supply of Radium Emanation from the Soil 

 to the Atmosphere. By Louis B. Smyth, B.A., Assistant 

 to the Professor of Geology in the University of Dublin t. 



[Plate XIV.] 



THE present investigation was undertaken as an extension 

 of similar work carried out by Professor Joly and 

 myself last summer J. 



In the course of that work the amounts of radium ema- 

 nation contained in the gases diffused through the soil were 

 estimated for various depths, and from day to day ; and 

 observations were made on the amount escaping from the 

 surface of the soil. The short series of observations thus 

 obtained, besides showing that the amounts of emanation 

 found to be escaping from the soil are quite adequate to 

 account for the amounts found in the atmosphere, appeared 

 also to show that " progressive variations in the amount of 

 emanation exhaled from the soil are attended by progressive 

 changes in the other direction in the amount of emanation 

 accumulating beneath the surface/' and that " fine weather 

 tends to diminish, and wet weather to increase the richness of 

 the ground gases." 



It was thought desirable to obtain a longer and more 

 regular series of simultaneous experiments on the amounts 

 of emanation being exhaled and accumulating respectively. 

 Consequently two series of experiments were started on 

 August 16th last year, and carried on simultaneously every 

 two days until March 5th this year. One series dealt with 



* Experiment seems to show that of two solutions for which the 

 quantity — T^rfac has the same value, the more dilute has the greater 

 foaming power. This indicates that the slowness of establishment of 

 equilibrium between the surface layers and the body of the film is a 

 factor of importance in the case of very dilute solutions. 



f Communicated by the Author. 



j Proc. Royal Dublin Society, xiii. p. 148, Aug. 1911. 



