73 KANSAS UNIVERSITY QUARTERLY. 
The flame was turned low, not over five centimetres in hight. 
The flame was placed between the poles of an electromagnet, A. 
By means of a screen, B, with a.75 cm. hole, light was used from 
that portion only of the flame which was just between the pole 
pieces. 
J 
Fig. 1. 
The general arrangement of the interferometer is shown in Fig. 
t. Light from the flame C is rendered slightly convergent by the 
collimating lens D and falls upon the semi-silvered surface E of a 
plane parallel glass F. Here the beam of light is divided, one 
part (approximately half) being transmitted to the mirror G, the 
other part reflected to the mirror H. After reflection at the mirrors 
G and H the two pencils reunite at the surface E; part of the first 
pencil being reflected and part of the second transmitted to the 
telescope K or to the unaided eye. 
The two plane parallel glasses F and L are set at an angle of 
45° with the mirrors G and H, and the distances of the two mirrors 
G and H from the semi-silvered surface E are at first made approx 
imately equal by turning the screw M. ‘The parallel glass L acts 
