DR. EVERETT ON THE RIGIDITY OF GLASS. 
14-7 
i(4 
Pointer at 165° 
Torsion 406^ 
Flexure 277, 
5501 
2(4 
55 
195° 
„ 406 
„ 276, 
551 
3(4 
55 
225° - 
„ 4091 
„ 272, 
547 
i(4 
55 
255° 
„ 410" 
„ 276, 
552 
to 
55 
285° 
„ 408 
„ 279, 
554 
3(4 
55 
315° 
„ 4041 
„ 282, 
5521 
From these we have the following means — 
1 (a){b). Torsion 408-1 Flexure 276-5, 551-2 
2 \a) \b). „ 407-0 „ 277-5, 552-5 
3 (a) (4 „ 407-0 277-0, 549-8 
Correcting for difference of scale-divisions, we derive the following values of Poisson’s 
ratio. 
From torsion at 100 grms. compared with flexure at 100 grins., 
•468, -459, -461. 
From torsion at 100 grms. compared with flexure at 200 grms., 
•473, -465, -473. 
Collecting all the results obtained with the brass rod, we find the mean value of T to 
be 406-4. 
the three results for weights of 200 grms. 551-2. We shall denote these two numbers 
by Fj and F 3 respectively. 
Eeduced to centimetres, these become 
TX^¥a=10-19, Fj x 7 i 5 1 o% = 6'97, F a x*m=13*90, 
which, being divided by 86 5 -4 or twice distance of scale from mirrors, give as the amounts 
of torsion and flexure in circular measure, 
Torsion, -01178; Flexure, -00805 and -0161. 
The whole length of rod operated on was in the present case of the portion 
between mirrors ; hence the values of $ for the mechanical correction are -§|-§- of the 
above angles, or 
•0229, -0157, -0313. 
(W+ w)a 
The values of the factor - — ^ — are respectively 
•729, -729, -442, 
giving as the values of the mechanical correction 
+ •0167 T, +-0114 F 15 +-0138 F 2 . 
The first optical correction is the same as for July 17th and 18th, viz. 
-•0025 T, -*0013 F„ — 0013 F 2 , 
