78  Mr.  Veley  on  an  Apparatus  for  Determination 
Method  of  Working. 
Firstly,  an  observation  was  made  with  both  condensers 
with  air  as  dielectric,  the  disk  o£  one  (on  the  right  hand, 
called  R)  being  clamped  in  a  fixed  position,  and  the  distance 
of  the  disk  of  the  other  (on  the  left  hand,  called  L)  from  the 
upper  surface  o£  the  dish  being  varied  by  the  micrometer- 
screw,  -until  the  minimum  sound  in  the  telephone  was  attained. 
Secondly,  the  liquid  to  be  experimented  with  was  then 
introduced  into  the  R  condenser  by  means  of  a  pipette  (the 
dish  being  slightly  tilted  to  avoid  the  inclusion  of  air-bubbles) 
to  the  point  at  which  the  surface  of  liquid  was  level  with  the 
bottom  of  the  rim  of  the  disk,  when  the  dish  was  replaced  in 
a  vertical  position.  Superfluous  liquid  accidentally  intro- 
duced was  removed  by  the  pipette  or  blotting-paper.  The 
distance  of  the  disk  from  the  dish  in  the  L  condenser  was  varied 
by  the  micrometer-screw  until  the  minimum  sound  was  again 
attained.  The  ratio  of  the  distance  of  the  disk  in  the  second 
observation  to  that  in  the  first  is  the  ratio  of  the  dielectric 
constant  of  the  liquid  to  that  of  air  (  =  1).  Hence,  therefore, 
as  explained  above,  thejdielectric  constants  can  be  determined 
in  terms  of  a  length,  measured  by  one  micrometer-screw. 
Two  sets  of  observations  of  the  first  operation  are  quoted 
to  show  the  degree  of  accuracy : — 
First  Set. 
L  (Air)  condenser.  R  (Air)  condenser  fixed  at 
Scale  Headings.  .7*615  mm.  on  scale, 
8-650 
8-645 
8-645 
8-710 
8-681 
The  mean  value  of  the  readings  of  the  L  condenser  is 
8-666  +  -0086. 
Second  Set. 
L  (Air)  condenser.  R  (Air)  condenser  fixed  at 
Scale  Readings.  12 '595  mms. 
14-05 
14-12 
14-13 
14-11 
14-12 
14-15 
14-12 
Mean    14' 12 
