Configurations formed by Floating Magnets. 103 



5a a pentagon. Six magnets give Qa and 6 b. With eight 

 magnets we obtain three configurations, 8a, 8 b. and 8 c. Now 

 the different configurations formed of the same number of 

 magnets always exhibit different degrees of stability. Vibra- 

 tion of the less stable forms (produced by alternately lifting 

 and lowering the superposed magnet) sends them into the 

 stable forms. Thus, bb on vibration rearranges itself into 5 a, 

 6 b into 6 a, and 8c or 8b into 8 a. With the configurations 

 of higher classes (the tertiaries, quaternaries, &c), even a 

 knock on the table is sufficient to cause the needles of the un- 

 stable configuration to move to positions of stable equilibrium. 

 On looking at the diagrams, it will be observed that only 

 the stable primaries form the nuclei of the secondaries ; and, 

 moreover, those primaries which are not dimorphous, like 2, 

 3, 4, and 7, serve as nuclei to more than one secondary. Thus, 

 2 is the nucleus of 8a, 85, 8c, 9, and 10b ; 3 is the nucleus 

 of 10a and 11 ; and 7 is the nucleus to 16, 17, and 18; while 

 each of the other stable and dimorphous primaries, 5 a, 6 a, and 

 8 a, appears only once as nucleus, respectively to 14, 15, and 

 18b. This same power of the most stable nuclei to resist out- 

 side stress is shown in the configurations of the tertiary and 

 quaternary classes," where the secondary 11 appears as nucleus 

 to 21, 22, 23, and 24. The secondary 18 a persists in even a 

 more marked manner as a nucleus. This 18 a has the contour 

 of that very stable 7 (the only configuration possible with 7 

 magnets) which forms its nucleus. Among the tertiaries 18 a 

 is the nucleus of 30 b, 31, 32, and 33 ; while in the quater- 

 naries it forms the inner nucleus of 46, 47, 48, and 49. The 

 fact of the persistence of these stable forms as nuclei may be 

 suggestive to chemists and crystallographers. 



It is here to be remarked that (as a general rule holding 

 good in all the classes), of two configurations made up of the 

 same number of magnets, that configuration is the more stable 

 which has the least number of needles for its nucleus. 



Illustrations of Molecular Structure. (1) Unstable Mole- 

 cular Equilibrium. — That the molecules in a body may be in 

 a state of unstable equilibrium so delicately balanced that a 

 slight extraneous action of pressure, heat, light, &c. may 

 cause a new molecular arrangement in the body, is shown in 

 many facts. A few of the more familiar ones will answer for 

 our purpose. Thus quiet water, which remains liquid at a 

 temperature of 10° C. or more below 0° C, changes suddenly 

 into ice when agitated ; and during this solidification its tem- 

 perature rises. In like manner a supersaturated solution of 

 disodium sulphate solidifies when a crystal of this substance is 

 dropped into it. Another instance of a sudden change from 



