[eve] primary and secondary gamma rays si 



that the rays will partly consist of a soft type, and indeed the shape 

 of this curve (fig. 6) is such that it lies between curves I. and II., 

 fig. 5, that is, between the curves for uranium and secondary y. 

 It will be remembered that the uranium y rays in my experiment 

 vvere hardened by passage through the uranyl nitrate itself which 

 contained the radiating Uranium X. If more lead had been used 

 by Hackett his curves would, I think, resemble those in figure 3. 

 It is still an open question how near the points lie to a definite curve. 

 So far as I can judge, repeated observations and increased care in 

 attention to details tends to bring the points nearer and nearer the 

 curves in this paper, which for soft rays are nearly parabolic. 



