A, A. Michelson — Velocity of Light. 393 
The direction of rotation was right-handed. te eliminate 
h 
making the rotation left-handed, and the deflection was meas- 
ured in the opposite direction. The results agreed well with 
those previously obtained with the mirror erect. 
o eliminate errors due to a regular variation in speed during 
every revolution, if any such could exist, the position of the 
frame was changed in several experiments. The results were 
the same as before. 
To test the question as to whether or not the vortex of air 
about the mirror had any effect on the deflection, the spe 
was lowered to 192, 128, 96, and 64 turns per second. If the 
vortex had any effect, it should have decreased with the lower 
speed, but no such effect could be detected. This also hohe 
that any error due to distortion of the mirror must be excess- 
ively small, otherwise it also would have been dintinighed with 
the smaller speed, thus giving different results. 
Finally, to test if there were any bias in making the obser- 
vations, the readings in several sets were taken by another, and 
ya ne down, without divulging them. The separate readings 
as consistent as when made by myself, and the results 
still agreed with those of the other observations. 
Results of Observations. 
Every number is the mean of ten separate observations. 
299710 299820 299740 299790 289790 
299600 299800 2997 299710 299740 
299760 299820 299740 299710 299680 
2998%0 299800 299720 299720 299710 
299740 299740 299580 299700 299660 
299710 299660 299580 299670 299710 
299810 299710 299480 299660 299690 
299840 299740 299720 299640 10 
299840 299760 299830 299650 299770 
299740 299700 299810 299660 ‘ 
299860 299690 299740 299810 820 
299840 299650 299770 299820 299820 
299790 670 299710 ae 299710 
2995 99740 299730 
ci ; the 9740 299780 299810 
299670 299690 299740 299620 2999840 
299860 299660 299750 299740 299780 
299860 299650 299710 299750 299580 
99820 299620 299740 7 299560 
299820 299660 299740 - 299680 299610 
Mean result 29972 
Cor. for temp. ~ bed (of steel tape, scale and screw). 
ie of esi air 299740 
Cor. for v +80 
Vel. of light in vacuo 299820 kilometers per second. 
