DR. EVERETT ON THE RIGIDITY OE IRON AND COPPER. 
367 
T • T 
The resulting correction for p is +’0017 p, the application of which gives as the cor- 
rected determinations of <r, *266, *265, and *269, and we adopt the mean -267, 
The mean uncorrected values of T and F are 311*3 and 245*2, which, when corrected 
as above, become 313*2 and 246*3. 
For the torsional and flexural rigidities, we have 
£=445*6 x 100 x 55*77 X 28*69 X OH -v-T, 
f =445-6 x 100 x 55*77 X 28*69 x -i-F. 
Hence 
log £ = 9*70805- log T=7*21223, 
log/=9*70641- log F=7*31495. 
The rod having been cut at the places where the mirrors were attached, the middle 
piece was found to weigh 90*110 in air, and 77*658 in water at temperature 9°*9 C. 
The expansion of water at this temperature being 1*00026, we have for the volume of 
the piece 
12*452 x 1*00026=12*455, 
and for the specific gravity, 
90*110 -f- 12*455 =7*2347. 
The volume divided by the length, which was 28*66, gives 7rr 2 =*43458, r=*37193. 
Hence we have 
M=l, 374, 100, 000, 
n = 542,340,000, 
k = 982,180,000, 
<7 = *267. 
Experiments on Copper Rod. 
These experiments gave the following values for T and F : — 
Pointer- 
reading. 
T. 
F. 
Pointer- 
reading. 
T. 
E. 
0° 
365*0 
265*0 
90° 
365*8 
264*8 
30° 
365*2 
265*0 
120° 
364*7 
265*0 
o 
O 
50 
365*8 
264*7 
150° 
365*7 
265*2 
Combining positions at right angles, we have — 
From 0° and 90° . . T=365*4 F=264*9 
„ 30° „ 120° . . „ 365*0 „ 265*0 
„ 60° „ 150° . . „ 365*7 „ 264*9 
T 
The values of p corrected for difference of scale-divisions, are 1*374, 1*372, and 1*375. 
To find the mechanical correction, we have length between mirrors 28*72, length 
subject to torsion and flexure 45*5, height of scale 222*8. 
