458 Dr. R. C. Tolman on the 



A fuller discussion of these facts may with advantage be 

 deferred until some further experiments on the scattered 

 radiation, at present in progress, are completed. 



A striking point is specially emphasized in the case of 

 silver. It was pointed out in an earlier paper that the speed 

 with which the corpuscles emerge from a radiator depended 

 only upon the hardness of the exciting radiation, and not at 

 all upon the material of which the radiator was composed. 

 Consequently the speed does not depend at all upon the pene- 

 trating power of the Rontgen radiation characteristic of the 

 tertiary radiator, even though the emission of the corpuscular 

 radiation is evidently very intimately connected with the 

 emission of this characteristic Rontgen radiation. 



When the exciting beam is from tin (A, in Al = 4'33) both 

 the soft and the hard characteristic radiations are emitted by 

 silver. The ionization produced by the corpuscles accom- 

 panying the emission of hard tertiary X radiation is appro- 

 ximately equal to that produced by the corpuscles accom- 

 panying the soft X radiation. The curves giving the values 

 of the absorption coefficient of the corpuscular radiation, 

 consisting of these two systems of corpuscles, clearly indicated 

 that the corpuscles emerged with the same velocity in either 

 case, this velocity being the same as that with which cor- 

 puscles emerge from any of the other tertiary radiators when 

 excited by the secondary radiation from tin. 



In conclusion, I wish to thank Professor Wilberforce for 

 the interest he has shown throughout these investigations. 



I wish also to thank Mr. Mesham, M.Sc.,for his assistance 

 in carrying out some of the evperiments. 



The George Holt Physics Laboratories, 

 June 30, 1911. 



_ = 



XLIV. Non-JS ewtonian Mechanics*. — The Direction of Force 

 and Acceleration. i?z/ Richard C. Tolman, Ph.D., Instructor 

 in Physical Chemistry at the University of Michigan* . 



IF force is defined as the rate of increase of momentum, 

 the equation 



„ cl . N du . dm ,. s 



F=^(,»u) = „^ + _u . . . . (1) 



allows for a change in mass as well as a change in 

 * Communicated bv the Author. 



