S. R. Williams — Electromagnetic Effect. 



301 



more difficult to build. The measurements of the motion 

 of the mercury column due to electromagnetic action were 

 carried on by Mr. William Lyman, an advanced student in the 

 department. 



Mr. Lyman's Experiments. 



Five tubes were made by ourselves in the laboratory and 

 numbered 1, 2, 3, 4, and 5, respectively. The diameters in 

 millimeters of the vertical central tubes and the side arms were 

 as follows : 



Table I. 



No. 



1 



2 



3 



4 



5 



Vertical central 

 tube 



12-9 



6-8 



6-8 



3*55 



2-33 



Side tubes 



6-8 



6-8 



12-9 



3-55 



2-33 



These tubes were placed between the poles of a small elec- 

 tromagnet, whose pole faces were 101xT6 mm and the distance 

 between them 46 mra . The arrangement is shown in fig. 7. In 

 fig. 8 is shown the relation between the change in height of 



FI6.7 



