114 



Prof. Albert A. Michelson on 



A and B (fig. 2). The strength of the magnetic field was 

 approximately the same in the two cases. 



The green cadmium line, however, is both separated and 



broadened, and the blue line more than the green. The 



Fis:. 6. 



green line of mercury is rather interesting on account of its 

 complicated structure, and the results show that the general 

 effect of the magnetic field is to obliterate details of structure, 

 changing the form to a simple doublet as in the other cases. 

 The separation and the broadening are nearly the same as 

 for the green cadmium line. 



Hydrogen in a vacuum-tube and lithium and thallium in 

 the blowpipe flame are but little affected. These lines are 

 all originally double, and in all three cases the only effect 

 observed in the magnetic field is a slight broadening and a 

 slight increase in the distance between the components. 



In all the preceding experiments the light was examined in 

 a direction at right angles with the magnetic field. When 

 sodium light was allowed to pass through cylindrical holes in 

 the pole-pieces so that the pencil Avas parallel with the field, 

 the same effect of separation of the line into two was observed, 

 and was even more clearly marked than in the transverse 

 direction, but the broadening was inappreciable. This 

 appears from an inspection of figs. 7 and 8. 



The fact that broadening occurs only or chiefly when the 

 pencil of light is at right angles with the field may possibly 

 be accounted for by an increase of velocity of the radiating 

 atom in this direction. This is what should be expected if 

 the atom is electrified and in motion ; for then a velocity at 

 right angles with the original one would be added, giving a 

 resultant velocity greater than before. The effect of this 

 increased velocity would be a displacement of the corre- 

 sponding spectral line proportional to the component of the 

 velocity in the line of sight due to the Doppler effect ; and 



