CONSTITUTION OF MATTEE BECQUEREL. 285 



electrons. But present day physics, in spite of the good results 

 which have been attained, is still far from affording a representa- 

 tion of an atom of matter. 



We have just seen that physics has attained a rather complete 

 knowledge of one constituent of matter, namely, the negative elec- 

 tron, and that the new ideas are based on the properties of this cor- 

 puscle. Now does there exist a positive electron, beside this negative 

 electron? It is evidently necessary that positive charges be present 

 somewhere in matter, but have they an atomic structure like the 

 negative charges, or are they of an entirely different nature ? 



In the discharges through media of rarefied gases and in the 

 emission of radioactive bodies, besides the negative rays, rays car- 

 rying positive charges are found, but these positive rays seem to be 

 in general entirely different from the former. 



When holes are pierced in the cathode of a Crookes tube, one may 

 observe behind the cathode sheafs of rays which have passed through 

 each one of the orifices formed, and which are propagated in a direc- 

 tion inverse to the cathode rays. These are the canalstrahlen dis- 

 covered by M. Goldstein. These rays are positively charged, and, 

 rather remarkably, whatever the gas in the tube may be, the meas- 

 urement of the ratio of the charge to the mass reveals only two sorts 

 of corpuscles (J. J. Thomson) some corresponding to the atom of 

 hydrogen carrying an elementary charge, and others corresponding 

 to the atom of helium and carrying a double charge. 



It is these last corpuscles which, in the emission of radium and all 

 radioactive bodies, form the a rays. Rutherford has demonstrated 

 by some magnificant experiments that these oo rays are made up of 

 atoms of helium. 



Lastly, there are other positive rays (anode rays) emitted by sub- 

 stances placed at the positive pole of a Crookes tube, which are no 

 other than material atoms which have lost their negative electrons 

 (Gehrke and Reichenheim). 



It may be seen, therefore, that the positive rays are quite different 

 from the negative rays ; they form a stream of electrified matter and 

 are made up, not of electrons, but of ions, material atoms deprived 

 of one or more negative electrons. These atoms are of a mass at 

 least equal to that of a positive ion of hydrogen, that is to say, an 

 atom of hydrogen charged positively in consequence of the loss of 

 a negative electron. In a word, the positive particles are the remains 

 of atoms. 



Because these positive charges remain in such a Avay affixed to 

 particles of matter, many men of science have not admitted the 

 existence of a positive electron similar to the negative electron. 

 Some have even thought that there is no positive electron and that 

 matter itself has an existence independent of electrons, that the union 



