596 Messrs. Miles Walker and W. Witcomb Stainer on the 



affected by the swirling action o£ the air. and it did not 

 communicate much force to B, because the natural period 

 time was 1/32 o£ the periodic time of B. 



Fis:. 3. 



B. Suspended disk of porcelain. 



E. Sheet-iron cover. 



1. Mirror attached to disk. 

 J. Bifilar suspension. 



2. Clamp for bifilar suspension. 



8. Suspended screen. 



7. Glass bottom of screen. 



9. Trifilar suspension for screen. 



3. Mirror attached to screen. 



1. Brass frame to change distance 

 between trifilars. 



4. Adjusting screws for trifilar. 



5. Bracket enabling the screen to 



be built around the disk. 



6. Limiting stops. 



10. Iron tube protecting the suspen- 



The procedure in making the experiment was as follows : 

 The disk B was brought as nearly as possible to rest. The 

 residual motion was usually a slow swinging motion which 

 followed strictly a sine law over one or two scale-divisions. 



