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VIII. The Scattering and the Absorption of the Gamma Rays. 

 By M. Ishino, Rigakushi {Kyoto Imperial University, 

 Japan), Research Student of Victoria University of 

 Manchester *. 



Contents. 



§ 1. Introductory. 



§ 2. Principle of the Method for the Determinations of 

 the Scattering-coefficient and the true Absorption- 

 coefficient. 



§ 3. Experimental Details. 



§4. Results. 



§ 5. Conclusions. 



§ 1. Introductory. 



IT is well known that the gamma rays are scattered in 

 their passage through matter. The nature of the 

 scattered rays has been studied by Kleeman f, Madsen %, 

 Florance §, and Gray ||. Florance made a careful investi- 

 gation of the amount of scattering in different directions 

 with the incident beam, and drew attention to the variation 

 in penetrating power of the radiation scattered in different 

 directions. 



Measurements of the absorption coefficient of gamma rays 

 from radium in passing through matter have been made by 

 a number of investigators, including Sir E. Rutherford ^[, 

 McClelland**, Eve ft, Wiegger %%, Tuomikoski §§, Soddy 

 and Eussell || ||, Florance %%, Oba ***, and Mr. & Mrs. Soddy 

 and Russell ftt- The values of the absorption coefficients, 

 obtained by the ordinary methods, show considerable 

 variation depending upon the conditions of measurement. 



* Communicated by Sir E. Rutherford, F.R.S. 

 t Kieeman, Phil. Mag. xv. p. 638 (1908). 

 % Madsen, Phil. Mag. xvii. p. 423 (1909). 

 § Florance, Phil. Mag. xx. p. 921 (1910) ; xxvii. p. 225 (1914). 

 || Gray, Phil. Mag. xxvi. p. 611 (1913). 

 II Sir E. Rutherford, Phys. Zeit. iii. p. 517 (1902). 

 ** McClelland, Phil. Mag. viii. p. 67 (1904). 

 ft Eve, Phil. Mag. xvi. p. 224 (1908) ; xviii. p. 275 (1909). 

 XX Wiegger, Jahr. Radioakt. ii. p. 430 (1905). 

 §§ Tuomikoski, Phys. Zeit. x. p. 372 (1909 j. 

 || l| Soddy and Russell, Phil. Mag. xviii. p. 620 (1909). 

 Iff Florance, Phil. Mag. xxvii. p. 225 (1914). 

 *** Oba, Phil. Mag. xxvii. p. 601 (1914). 

 ttt Mr. & Mrs. Soddy and Russell, Phil. Mag. xix. p. 725 (1910). 



Phil. Mag. S. 6. Vol. 33. No. 193. Jan. 1917. K 



