CONSTITUTION OF MATTEE BECQUEREL. 287 



Other experiments on discharges in very rarefied gases made first 

 by M. Lilienfeld and then in another form in our laboratory have 

 resulted in obtaining positive rays which may be interpreted by sup- 

 posing the existence of free positive electrons, but other interpreta- 

 tions have been opposed to this hypothesis, and further researches in 

 this direction must be made. 



It is therefore possible that there exists a positive electron of the 

 same nature as the negative electron. I say " of the same nature " and 

 not "identical," because the dissimilarity between the phenomena 

 presented by the two electricities renders it probable that there is a 

 difference between the two electrons. If the two sorts of electrons do 

 exist, according to our experiments they should have the same ratio 

 of charge to mass, but their masses as well as their charges may be 

 very different. 



One fact is certain in any case, and this is that the positive electrons 

 if they exist, are very tightly bound to the atoms of matter. They 

 only reveal themselves in magneto-optic phenomena, where the 

 physicist carries his investigations to the very foundation of the atom 

 without breaking it up, or in the interior of tubes of rarefied gases 

 under very special conditions where positive ions are broken up by 

 the shock of the cathode particles acting in the capacity of projectiles. 



We can see from this how much the ideas on the nature of positive 

 charges have been modified. Yet whatever the positive electron may 

 be, its nature must be known as well as the negative electron before it 

 is conceivable to understand the structure of an atom of matter. 



Nevertheless there are two very interesting systems of explanation 

 which have been developed. Some physicists have conceived the idea 

 that at the center of the atom is a positive charge around which the 

 negative atoms gravitate like planets around the sun. But this 

 hypothesis meets with grave difficulties which I can not set forth 

 here. I think that one should not allow himself to be led astray by 

 the seductive idea of a similarity between the world of the infinitely 

 small and the world of the infinitely great and it seems to me that a 

 group of atoms is in no way comparable to the world of matter. 



The system most generally adopted to-day is as follows: 



It is imagined that there is a positive charge uniformly distributed 

 over a sphere in the interior of which are situated the negative 

 electrons. The positive charge is equal to the sum of the charges of 

 the negative electrons. The positive electricity tends to draw the 

 corpuscles to the center of the sphere but the mutual repulsion of the 

 negative electrons drives them away from this point and they take 

 up a position of equilibrium and group themselves regularly about 

 the center. 



By a simple experiment due to Prof. Mayer, we can reproduce a 

 similar grouping. If we take a number of small steel needles iden- 



