404 FRAGMENTS OF SCIENCE 



gion which harmonized with my speculative tastes. It was 

 essentially an inquiry in molecular physics, having refer- 

 ence to the curious, and then perplexing, phenomena ex- 

 hibited by crystals when freely suspended in the magnetic 

 field. I here lived amid the most complex operations of 

 magnetism in its twofold aspect of an attractive and a re- 

 pellent force. Iron was attracted by a magnet, bismuth 

 was repelled, and the crystals operated on ranged them- 

 selves under these two heads. Faraday and Pliicker had 

 worked assiduously at the subject, and had invoked the 

 aid of new forces to account for the phenomena. It was 

 soon, however, found that the displacement in a crystal 

 of an atom of the iron class by an atom of the bismuth 

 class, involving no change of crystalline form, produced a 

 complete reversal of the phenomena. The lines through 

 the crystal which were in the one case drawn toward the 

 poles of the magnet, were driven, in the other case, from 

 these poles. By such instances and the reasoning which 

 they suggested, magne-crystallic action was proved to be 

 due, not to the operation of new forces, but to the modifi- 

 cation of the old ones by molecular arrangement. Whether 

 diamagnetism, like magnetism, was a polar force, was in 

 those days a subject of the most lively contention. It was 

 finally proved to be so; and the most complicated cases 

 of magne-crystallic action were immediately shown to be 

 simple mechanical consequences of the principle* of dia- 

 magnetic polarity. 



These early researches, which occupied in all five 

 years of my life, and throughout which the molecular 

 architecture of crystals was an incessant subject of men- 

 tal contemplation, gave a tinge and bias to my sub- 

 sequent scientific thought, and their influence is easily 



