MATTER, SPACE, AND TIME 215 



poles pointing upward, and thus the magnets 

 were drawn towards the centre by the attraction of 

 the big magnet suspended above them, and at the 

 same time were repelled from the centre by their 

 mutual repulsions. Under the influence of these 

 two forces they assumed positions of equilibrium. 

 Mayer found that as long as the number of 

 little magnets was not more than five, they 

 arranged themselves in a single ring, but that, 

 on increasing the number to six, a discontinuity 

 of arrangement was observed ; the single-ring 

 structure ceased to be stable, and the magnets 

 placed themselves with five in a ring and one at 

 the centre. This two-ring configuration persisted 

 as more magnets were added, till the number rose 

 to fourteen, with five in the middle ring and nine 

 in the outer circle. With fifteen magnets this 

 arrangement in its turn became unstable, and a 

 three-ring system appeared. 



Thomson overcame the difficulties of the 

 mathematical analysis, and has shown that similar 

 phenomena of disposition must appear in the 

 system which, as described above, he imagines to 

 correspond with the atom. Here also, discon- 

 tinuities in arrangement will appear, and, when 

 certain definite numbers of electrons have come 

 together, an additional ring will be formed. 

 Periodic likenesses in structure also arise and will 

 give to the system in which they occur similarities 

 of periods of vibration, and, it was thought, might 

 explain the homologous series of lines which are 

 found in the spectra of elements lying in the 

 same group of Mendeleeffs periodic classification. 



So far the theory had been carried when this 

 book first appeared. But, as we shall see below, 



