342 RECORDS. 



Dr. Pegram's paper related to the generation of electrical 

 charges by radium, with special reference to the suggestion of 

 Soddy that when the a particles, carrying their positive charge, 

 are expelled from the radium, there is no corresponding nega- 

 tive charge left behind in the mass. A few milligrams of 

 radium bromide were enclosed in a thick lead capsule, which 

 was supported on a quartz rod in an exhausted vessel. Gold 

 leaves attached to this capsule gave no indication of a charge, 

 showing either that there was the usual generation of equal 

 amounts of positive and negative electricity when the a particles 

 are thrown off, if, as has been supposed, the number of a parti- 

 cles is much greater than the number of negatively charged 

 particles, or else that the number of 13 particles is about equal 

 to the number of a particles. It remains to try a similar 

 experiment with radium bromide which has been recently in 

 solution, and, therefore, sends off few of the /3 particles. 



Dr. Dudley referred to his previous communications to the 

 Academy, describing the stremmatograph tests, which afforded 

 tabulations of the recorded unit fiber stresses in the base of 

 rails, and their distribution under moving locomotives and cars. 



The determination from the unit fiber strains, of the negative 

 and positive bending moments of the rails, due to the passing 

 wheel effects, indicates that for a definite construction of the 

 superstructure of the permanent way, they are independent,, 

 partially, of the total load of the locomotive or car, but de- 

 pendent upon the type of each, in construction of wheel base 

 and wheel spacing, in loading the foundation. 



In a series of stremmatograph tests, on the New York Cen- 

 tral and Hudson River Railroad, near mile post No. lo, De- 

 cember 23 and 30, 1899, locomotive No. 870, an eight-wheel 

 type of engine, weight, 220,000 pounds, drawing the " Empire 

 State Express " of four cars, weight, 430,000 pounds, at speeds 

 of 42 and 44 miles per hour, the average positive bending mo- 

 ments for the engine were 12.40 inch-pounds per pound of 

 static load, for one rail, constrained by a negative bending mo- 

 ment of 1.88 inch-pounds. 



The average positive bending moments for the entire loco- 



