Quadrant-Electrometer. 301 
10 Daniells ; 8=1808 :— 
Deflection observed = 437°0, 
» calculated =438°7. 
A was now insulated and post raised, and B was connected 
to 30 Daniells ; 6=5468 :— 
Deflection observed =785, 
» calculated =792. 
The post of A was lowered to contact and B connected to 
10 Daniells ; 2=1808 :-— 
Deflection observed = 408, 
»  calculated=410. 
The next experiment was similar, excepting only that the 
insulated quadrant B was connected to a condenser ; this con- 
denser consisted merely of a brass tube insulated within a 
larger tube—its capacity is about 0°00009 microfarad. The 
jar was at its standard charge. Calling the capacity of the 
condenser 6, in terms of our temporary unit, we have, as 
before, age ae 
gaol tatia—t (yt). 
b+at 722 +1 
When @=1259, @ was observed to be 927, whence b=3°159. 
We are now in a position to obtain independent verifica- 
tion of the values already obtained for the constants. Suppose 
A be connected to the case, that condenser } is charged trom 
a battery of known potential, such that it would give deflec- 
tion @ if connected to B, and the charged condenser is then 
connected to B. Suppose W be the deflection before con- 
nection is made, ¢ after. Then 
b(O—b)={92+at1}(p—y). 
When 6=1439 and w=0, it was found that 6=915. The 
value of ¢, calculated from the values of the constants already 
obtained, is 928. 
When @=1439 and w=—676, it was found that 
@= +676; the calculated value is 688. 
A further experiment of verification, involving only the 
capacity of the quadrant, is the following. The quadrant A 
being connected to the case, B was charged by contact in- 
stantaneously made and broken with a battery of known 
potential, and the resulting deflection was noted. ‘The in- 
stantaneous contact being made by hand, no very great 
accuracy could be expected. Let W and ¢ be the readings on 
the scale before and after the instantaneous contact; then 
6—¢ 1 3 
——_ = = |-345: 
P—-F Q2ta 
Phil. Mag. 8. 5. Vol. 19. No. 119. April 1885. ¥ 
