784 ANNUAL EEPORT SMITHSONIAN INSTITUTION^ 1908, 



phenomena follow the same laws as those of the salts of radium in 

 solution and that the nitrate crystallizes reactive after a time. It 

 seemed then that uranium has an emanation. He showed that the 

 double sulphate of uranium and potassium is spontaneosuly luminous 

 in the dark like the radium salts, only the effect is far smaller than 

 was expected. Becquerel proved that the phenomenon of Crooke's 

 spinthariscope is due to the cleavage of the hexagonal blende under 

 the bombardment of the a rays. 



Becquerel considered with Curie that the radio-active phenomena 

 are due to a constant evolution of the atom, the atoms of the active 

 bodies being variable and constantly destroj^ed by explosions. The 

 debris may be in part of inert matter, partly of groups of electrons 

 or single electrons which constitute the various emanations, the a 

 and the fi rays, and communicating to the ether concussions (y rays). 

 The corpuscles remain scattered in matter or in space. According 

 to this theory the emanation may be regarded as a group of electrons 

 carried by gases or matter. Perhaps, as Filippo Re believes, we may 

 consider the radio-active atom as a condensing solar system ; perhaps 

 with Perrin, as a solar system from which the exterior planets are 

 escaping. Becquerel said of these hypotheses : " Re's may be consid- 

 ered of equal worth w^ith the inverse hypothesis; they both deserve 

 the interest due attempts to connect by common laws the infinitely 

 small atom with the infinitely great universe. 



DIVERSE RESEARCHES. 



Along with these great problems, in which Becquerel held such a 

 leading position, he worked on certain other problems which the 

 greater ones had temporarily replaced : His research with Edmond 

 Becquerel on the temperature of the sun ; then in 1879, on the mag- 

 netic properties of nickel and cobalt ; then he shovvcd by interference 

 methods that in the propagation of radiations across rotary-polariz- 

 ing magnetic fields the right and the left circularly polarized com- 

 ponents travel with different velocities. Later, when the Zeeman 

 effect was discovered, he took up his latest ideas relative to the action 

 of the magnetic field upon light and showed the connection between 

 the Faraday and the Zeeman phenomena. Then, in collaboration with 

 Deslandres, he studied these phenomena experimentally, particularly 

 with iron. They showed that, in this case, certain rays are unaffected, 

 some give triplets, other quadruplets. The ray, 0.3865 /x, is anomalous ; 

 the two extreme rays are perpendicularly polarized to the lines of 

 force, the other two parallel. 



Becquerel also showed in a beautiful way the anomalous dispersion 

 of sodium vapor by the classic method of crossed-prisms spectro- 

 scopes, but with a very original disposition of the apparatus. He 



