Vol. 6, 1920 
PHYSICS: C. BARUS 
499 
my first observations were made with such an apparatus; and adequate 
air damping was secured by hanging the Hght scale pans in dash pots. 
Readings were made on a large graduated circle (torsion head), the stopsjof 
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which were micrometer tangent screws. Changes of twist registered by 
the interference fringes were evaluated either by the latter, or by the 
micrometer screw of the rectangular interferometer. 
If the weight remains on one side, viscous deformation not only grows 
