Effect of Ionization of Air on Electrical Oscillations. 213 



This method again may be applied to the beam with end 

 loading, thus amine (fig. (>) is the primary deflexion diagram 

 for a beam of two spans under a uniform load, in which the 

 centre span has sunk by an amount S. Find the charac- 

 teristic points S 2 , T 2 , at each side of the support b, carefully 

 bearing in mind that area akbm is the one to be used in the 

 expression for the distance of the characteristic point from the 

 base-line ac. Next modify these characteristic points in 

 accordance with the formula? already considered in reference 

 to continuous beams under lateral loading only. 



Conclusion. — It will be seen that the method of successive 

 graphical approximation is applicable to beams under end- 

 long and lateral loading either continuous or discontinuous. 

 The end load may or may not pass through the centrode of 

 the beam section. For large columns under practical 

 conditions it is usually unnecessary to take into account the 

 moments due to lateral deflexion, but under special circum- 

 stances of slender columns these moments may become of 

 importance. For a simple system of loading on a beam 

 of one span only the analytical method of solution presents 

 many advantages, but if the lateral loading is complicated 

 by the presence of unsytnmetrical concentrated loads or by 

 distributed loads of varying intensity, the graphical method 

 is shorter and easily applied. For an analysis of a beam or 

 tie continuous over several supports and subjected to end- 

 long loadings it is_, although long and complicated, the only 

 method available. 



XXI. The Effect of Ionization of Air on Electrical Oscillations, 

 and its bearing on Long- Distance Wireless Telegraphy *. 

 By Prof. G. W. 0. Howe, Imperial College, South 

 Kensington |. 



WHILE it is true that Dr. EceW theory of the 

 refraction of electromagnetic waves in the upper 

 atmosphere is based on the assumption that ionization makes 

 the atmosphere conducting, it must not be overlooked that 

 this conductivity must, as Dr. Eccles has shown, be of a 

 different type to that of ordinary materials, if it is to account 

 for the observed phenomena. When a charged ion of 

 molecular mass is situated in an alternating electric field 



* See Paper with tins title by Prof. Barton and Mr. Kilbv, Fliil. Mag. 

 Oct. 1913, p. 567. 



f Communicated by the Author. 



