302 Dr. J. Hopkinson on the 
The following results were obtained :— 
6. pr. @ observed. ¢ calculated. 
1796 0 763 765 
1796 —A93 493 482 
We next determine the coefficients q,, and go, of induction 
of the induction-plate on the quadrants. This is easily done 
from the deflections obtained with the induction-plate, one or 
both pairs of quadrants being insulated. First, suppose one 
pair, say B, are insulated whilst A is connected to the case :— 
0O=+ G2 B—qu D—fpd, 
o= — pB, 
d= p,D 2 
whence ha, iy 
Ps oot Bu? 
@ being the deflection actually observed, and 6 that which 
the battery used would give if connected direct to the quad- 
rants, the needle having the standard charge. When @ was 
12,800 and w=ps, d was 418, whence go,=0°0504. 
In the same way A being insulated but B connected to 
the case, @ was found to be 43°6, whence g,,=0°00508. 
Again, when both quadrants are insulated we have 
O0= gquA—gqeB—quD+ Bp, 
O= —qpA + Go2B—guD —Bud, 
p=(A—B), 
d=p;D. 
From the first two equations, 
(911923 — 9}2)(A—B) —{(G22— G12) 914 — (Gu — 912) 924} D 
+ (922+ Gu—2412)Bub=0 ; 
¢= ott. (G22 — 912) 1a — (911 — G12) Goa 
Mg (911902 =O) + (Goo+ 91 — 2012) Be? 
In the case when w=ps, substituting the values already 
determined, we have 
whence 
b=8x 0°0142; 
it was observed with 6=12,800 that 6=183 ; the calculated 
value would be 182. 
With a lower charge on the jar, viz. when p=p; x 0°805, 
with B insulated, A connected to the case, and 6=12,800, it 
was found that 6=437°5 ; the calculated value is 441. 
The capacity qi, of the induction-plate is of no use; its 
value, however, is about 0-004, in the same unit as has been 
so far used. 
