C. Barus — Displacement Interferometer. 



Ill 



The inside of j or Q prolonged is ground and receives the 

 hollow cylindrical plug i of the table I and this may be 

 clamped by the set screws *'. 



u Upon I stands the grating G secured by the screw g to the 

 ring-shaped support H, which reposes in an annular gutter in I 

 on three leveling screws. Moreover a spiral spring (not shown) 



Figs. 1, 2, 3. 



,m 



fig.i. V 



m the inside of the hollow conical tube i, pulls down the ring 

 H firmly upon /, so that nothing is liable to fall on transporta- 

 tion. The ruled surface of the grating G is toward the light 

 or collimator A and in the axis of rotation. The adjustment 

 need not be very accurate. The rulings are parallel to the 



Certain details of the parts of the apparatus may now be 

 pointed out. The collimator A may be raised or lowered on 

 its vertical stem or clamped in any position by aid of the wing 

 nut, «', on a longitudinally split tube. It may also be slightly 



