384 FKAGMENTS OF SCIENCE. 



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 characterised 

 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 ration- 

 alism without their standing to each other in the rela- 

 tion of cause and effect. 



My first really laborious investigation, conducted 

 jointly with my friend Professor Knoblauch, landed 

 me in a region which harmonised with my speculative 

 tastes. It was essentially an enquiry in molecular 

 physics, having reference to the curious, and then per- 

 plexing, phenomena exhibited 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 repellent force. Iron was 

 attracted by a magnet, bismuth was repelled, and the 

 crystals operated on ranged themselves 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 towards 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 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 



