474 
PHYSICS: A. A. MICHELSON 
Proc. N. a. S. 
The tremors of such a surface which would otherwise make observa- 
tions impossible, are avoided by the simple device of amalgamating the 
FIG. 2 
surface of the shallow dish and covering with a layer of mercury a half 
millimeter or less in depth, whereby the vibrations are very rapidly ex- 
tinguished. A photograph of the instrument is shown in figure 2. 
ON THE APPLICATION OF INTERFERENCE METHODS TO 
ASTRONOMICAL MEASUREMENTS 
By a. a. MichKlson 
Rye;rson Physicai. Laboratory, University of Chicago 
Read before the Academy, April 26, 1920 
In order to test the practicability of using an interferometer with large 
base, for the purpose of measuring close double stars, and possibly the 
