634 FRAGMENTS OF SCIENCE. 



their disciples? Because they assumed, and were justified 

 in assuming, that those whom they addressed had that 

 within them which would respond to their appeal. If 

 Germany should ever change for something less noble the 

 simple earnestness and fidelity to duty, which in those days 

 characterized her teachers, and through them her sons 

 generally, it will not be because of rationalism. Such a 

 decadent Germany might coexist with the most rampant 

 rationalism without their standing to each other in the 

 relation of cause and effect. 



My first really laborious investigation, conducted jointly 

 with my friend Professor Knoblauch, landed me in a 

 region which harmonized with my speculative tastes. It 

 was essentially an inquiry in molecular physics, having 

 reference to the curious, and then perplexing, phenomena 

 exhibited by crystals when freely suspended in the mag- 

 netic field. I here lived amid the most complex operations 

 of magnetism in its twofold aspect of an attractive and a 

 repellent 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 com- 

 plete 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 modification 

 of the old ones by molecular arrangement. Whether 

 dia magnetism, 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 

 diam ague tic 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 mental contemplation, gave a tinge and bias 

 to my subsequent scientific thought, and their influence 



