Motion of the Medium on the Velocity of Light. 385 

 Observations of the double displacement A. 







1st Series. 



1 = 



3-0 



22 meters. 















6 = 



8-7 



2 meters per second. 









A 



= double displacement ; 



w = weight of observation. 





A. 



w. 



A. 



iv. 





A. 



IV. 



A. 



w. 



.510 



1-9 



•521 



0-9 





•529 



06 



■515 



2-5 



■508 



1-6 



■515 



•9 





•474 



2-0 



•525 



2-7 



•504 



1-7 



•575 



•6 





•508 



1-4 



•480 



•8 



•473 



1-4 



•538 



2-1 





•531 



•8 



•493 



106 



•557 



•4 



•577 



■6 





•500 



5 



■348 



2-8 



•425 



•6 



•464 



1-7 





•478 



•6 



•399 



5-7 



•560 



2-8 



•515 



1-2 





•499 



1-0 



•482 



2'1 



•544 



■1 



•460 



•4 





•558 



•4 



•472 



2-0 



•521 



•1 



•510 



•5 





•509 



2-0 



•490 



•8 



•575 



•1 



•504 



•5 





•470 



2-1 











2d Series. 



1 = 



6-151, 6 = 



7-65. 







A. 



w. 



A. 



w. 





A. 



w. 



A. 



w. 



■789 



4-9 



•891 



1-7 





•909 



1-0 



•882 



6-6 



•780 



3-5 



•883 



2-5 





•899 



1-7 



■908 



5-9 



•840 



4-6 



•852 



11-1 





•832 



4-3 



•965 



20 



•633 



1-1 



•863 



1-5 





•837 



2-1 



•967 



3 3 



•876 



7-3 



•843 



1-1 





•848 



1-9 







•956 



36 



•820 



3 4 





•877 



4-7 











3d Series. 



I — 



6-151, = 



5-67. 







A. 



w. 



A. 



w. 





A. 



w. 



A. 



IV. 



•640 



4-4 



•626 



11-9 





•636 



31 



•619 



6-5 



If these results be reduced to what they would be if the tube 

 were 10 m long and the velocity l m per second, they would be 

 as follows : 



Series. A. 



1 -1858 



2 -1838 



3 -1800 



The final weighted value of A for all observations is A= -1840. 

 From this, by substitution in the formula, we get 



x 



= *434 with a possible error of ±"02. 

 = -437. 



The experiment was also tried with air moving with a 

 velocity of 25 meters per second. The displacement was about 

 Y^-fl- of a fringe ; a quantity smaller than the probable error of 



observation. The value calculated from 



?? a — 1 



would be -0036. 



It is apparent that these results are the same for a long or 



short tube, or for great or moderate velocities. The result was 



also found to be unaffected by changing the azimuth of the 



fringes to 90°, 180° or 270°. It seems extremely improbable 



that this could be the case if there were any serious constant 



error due to distortions, etc. 



Am. Jour. Sci— Third Series, Vol. XXXI, No. 185.— Mat, 1886. 

 25 



