368 WILSON— CONSTITUTION OF THE ATOM. [April 22, 



positive sphere is negligible. This theory therefore does not support 

 the view which is the basis of the *' principle of relativity," that all 

 phenomena are electromagnetic in character. The mass and rigidity 

 of the positive spheres are assumed to exist and cannot be explained 

 by electromagnetic forces. There is no reason why the motion of 

 these spheres through the ather should not produce effects capable 

 of being detected and which would enable us to determine the veloc- 

 ity of the earth relatively to the xther. The fact that this has not 

 yet been done does not prove that it is impossible. 



According to Sir J. J. Thomson's theory the properties of dif- 

 ferent atoms are due to the number and arrangement of the electrons 

 in the positive sphere. The problem of the distribution of 11 

 electrons in a positive sphere has not been solved and is very 

 complicated, so Sir J. J. Thomson investigated the much simpler 

 problem of the distribution of /; electrons in a plane wdien they are 

 all acted on by forces of attraction proportional to their distances 

 from a fixed point in the plane. 



This problem can also be solved experimentally by means of 

 Professor Mayer's floating magnets. The electrons arrange them- 

 selves in concentric rings. Thus six give a ring of five and one in 

 the middle. Seventeen give a ring eleven, a ring of five and one 

 in the middle. Thirty-two give rings of fifteen, eleven, five and one 

 in the middle. Forty-nine give rings of seventeen, fifteen, eleven, 

 five and one in the middle. 



With two in the middle we get a series of rings containing 8, 

 12, 16, 19 and 22 electrons respectively and a similar series with 

 three in the middle and so on. 



This leads to a very interesting suggestion with regard to the 

 series of elements which have similar properties for example: 



Helium, neon, argon, krypton, xenon; hydrogen, lithium, sodium, 

 potassium, rubidium, caesium ; fluorine, chlorine, bromine, iodine. 



Sir J. J. Thomson suggests that each element in such a series 

 may be derived from the one before it by the addition of another 

 ring of electrons the arrangement of the inner rings remaining un- 

 changed. This explains the similarity of the properties of the 

 elements in such series. 



On this view an atom of bromine is an atom of chlorine with the 



