THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. XXIX. — On the Corpuscular Rays produced in differ- 

 ent Metals by Rontgen Rays • by C. D. Cookset. 



Sag-nac* has shown that when Rontgen rays fall on a sub- 

 stance this substance gives off rays very like the Rontgen rays 

 producing them. Barklaf has investigated these rays and found 

 that those from gases and light solids were almost identical 

 in penetrating power with the primary rays producing them, 

 while those from heavy solids such as lead, zinc, copper, etc., 

 are much less penetrating than the primary. He also finds 

 that the rays from gases and light solids vary in penetrating 

 power as the primary varies, but those from the heavy 

 solids vary very little for a large variation in the penetrating 

 power of the primary. All these secondary rays are probably 

 pulses in the ether like Rontgen pulses, though the secondary 

 pulses may vary greatly in thickness from the primary produc- 

 ing them ; heavy metals giving out much thicker pulses than 

 the primary. Hereafter in referring to this type of rays we 

 shall speak of it as "Secondary Rontgen Rays." 



Beside this type of rays, Townsend,^; Dorn,§ and Curie and 

 Sagnac|| have shown that heavy metals, when Rontgen rays fall 

 on them, give out a very absorbable type of radiation, consisting 

 in part of negatively charged particles. The velocity of these 

 particles is of the order of that of the cathode particles in a highly 

 exhausted tube. Bestelmeyer^f has investigated by a photo- 

 graphic method the corpuscular rays produced when Rontgen 

 rays fall on a platinum plate and found that they have veloci- 

 ties from 0-195 to 0-327 of the velocity of light. He shows 



* Annales de Chirnie et de Physique, xxii, p. 493, 1901. 



fPhil. Mag., xi, p. 812, 1906. 



jProc. Canib. Phil. Soc, x, p. 217, 1899. 



gAbhand. d. naturf. Ges. zu Halle, xxii, p. 39, 1900. 



I Journal de Physique (4), i, p. 39, 1902. 



t Ann. der Physik, xxii, p. 429, 1907. 



Am. Jour. Sci.— Fourth Series, Vol. XXIV, No. 142.— October, 1907. 

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