S E V E N - F O L D LUMINOSITY. 95 



in the terrestrial and celestial spheres. It was found, for example, 

 that the flames from the poles of a large electro-magnet (which 

 were much larger and brighter than those emitted from the 

 permanent steel magnet) would, after the galvanic circuit was 

 completed, slowly and gradually resolve themselves into dis- 

 tinct stratifications of color, presenting, in fact, the seven-fold 

 luminosity of the rainbow, with the red below and the violet 

 above. These colors, again, were found to vary with the 

 varying distances at which they were viewed the whole of 

 the appearances, when taken together, showing that each one 

 of the differently colored radiations terminated, for the most 

 part, at a certain distance from the common center of lumin- 

 osity. This distance, though Reichenbach did not remark it, 

 was probably nearly the same all around; the differently 

 colored rays thus forming a system of concentric spheres of 

 light. 



Guarding against errors which might arise from variations 

 in these colors as resulting from the varying distances at which 

 they were viewed, our philosopher was now prepared for 

 another interesting step. Having previously found that a mag- 

 netic bar, with poles in the direction of the dip, always emitted 

 different colors from those it gave in the meridian, he pro- 

 ceeded to ascertain what effect other positions of Jhe pole 

 would have upon the character of the luminosity. For this 

 purpose he caused a magnetic bar to revolve lengthwise, first 

 in a vertical circle in the direction of the magnetic meridian, 

 then in a vertical circle in a direction east and west, and lastly, 

 in a horizontal circle. He found that in each case different 

 colors were evolved according as the magnet was pointed in 

 different directions, and that as it passed, in each case, through 

 a complete circle, it evolved, in regular succession, all the colors 

 of the rainbow ! 



