VELOCITY OF WHITE AND OF COLOURED LIGHT. 
257 
January 20, 1881, No. 6. 
Wheel. 
Clock. 
Reading. 
Differences. 
At mean reading. 
Reading. 
Alternate 
differences. 
Alternate second 
differences. 
231 
2,642 
7,449 
2,411 
2,404 
1,437 
5,046 
515 
9,890 
23,072 
32,309 
45,300 
54,433 
22,557 
(22,419) 
22,228 
22,124 
329 
295 
Signal at 3,810 
Signal at 24,108 
0-002406 
s=21,141 
4/= 331 
v= 11210 
Correction for friction, &c. = — -0028 
v= 1-1182 
w=-,=465*00 
V 
Referring to the mathematical theory of our method it will he seen that in order to 
calculate for each observation the slight correction which must be applied* owing 
to pp being not exactly equal to yf, it is necessary to make a first approximation to 
Db 
the velocity of light neglecting this small correction. Our formula for this first 
approximation, studying the 12th and 13th equality (which is the best pair for our 
purpose), is 
.y_2 m(n + ??/)D b 
The mean value of all our determinations of 
n-\-n' is 880*02 
D B =3*18845 
2m=800 
r=12 
log =2*9444922 
„ *5035796 
„ 2*9030900 
6*3511618 
1*0791812 
5*2719806 
V=187,060 
first approximation 
2 L 
MJDCCCLXXXIL 
