WITH THE CAVENDISH APPARATUS. 
219 
ings for the resting points 
where 
s=26e and s'=26e', 
TO 
A=jXC, 
D: 
? — si 
and C: 
26HE * 
: IV 2 
is called the general constant, which, combined with p, gives Cthe^pecm/constant. 
The resting points s and s' are not directly observed, and in strict accordance with 
the preceding theory, ought to be found thus. 
Let ff and o’ be the scale readings at the extremities of the arc of vibration, or 
when ju^+B=0 and sr respectively, 
a =i-j-26A cos 0 =a'-)- 26A, 
ff'=>y+26A cos n—s — 26A ; 
s — + 0 - 
We will now deduce a few values of A in strict accordance with the theory from 
the numerical values given by Mr. Baily, extracting the data furnished by observa- 
tion from his tables. 
1st Series. — 2-inch lead balls with bifilar silk lines ; distance * 177 inch. 
1841. 
No. 
Position of 
masses. 
Extreme divisions 
observed. 
Time of vibration. 
Mean of times. 
13 
Positive 
r 50-001 
L 177*50 j 
sec. 
501-782 
sec. 
501-434 
14 
Negative 
r i 7 o-oo\ 
t 27-50/ 
501-087 
Here s=113'9, s'— 9875 ; and D=^=7'575. 
log C = 6*360356 ; and .*. A=7'6103. 
Again, 
22nd Series. — 2^-inch hollow brass balls with single copper wire, diameter *0219 in. 
1841. 
No. 
Position of 
masses. 
Extreme divisions 
observed. 
Time of vibration. 
Mean of times. 
1084 
Positive 
r 86-201 
L 118-74 J 
sec. 
216-111 
sec. 
"j* 216-1105 
1085 
Negative 
117-701 
81-62] 
216-110 
Here s= 102-47, s' = 99*66 ; and D=^=l-405. 
log C = 6*354454 ; and A=7*5184. 
It is to be observed that Mr. Airy’s theory does not contemplate a difference in 
the time of vibration in different experiments with the same balls suspended in the 
same manner, and moreover the effect of resistance of the air is entirely omitted. 
2 f 2 
