24 Messrs. Henderson and Henry on the Motion 



other. We may therefore consider the space between the 

 strips to be filled with tubes of forces stretching horizontally 

 across perpendicular to the beams of light and moving along 

 in the direction of the transmitted beam. If these tubes of 



Fiff. 2. 





R,R= damping resistances. 



force drag the tether with them, a displacement as already 

 described should be observed in the interference-bands, when, 

 after being short-circuited, these parallel wires are suddenly 

 introduced into the circuit. 



In our experiments, however, we again failed to detect any 

 motion. At this point we may find what minimum velocity 

 of the aether would have been detected by this method. 



Let u = velocity of the aether, 

 v = „ „ light, 

 d = path of light in moving aether, 

 \ = wave-length of light used. 

 Then v + u = velocity of one beam, 



v — u = velocity of other beam ; 



— — = time taken by first beam to travel distance d, 



d 



v — u " 



2nd 

 ~2 o= difference of time occupied by the two 



beams in passing round the square. 



and 



second 



Denote this time by r. 



