EFFECTS  OF  CHANGE  OF  TEMPERATURE.  499

•0004  x  30  x  2irf*lK,  -0007  x  30  x  2-jrfz/K     But  the   Effects  of
electrical  work  done  in  charging  is  (p.  133  above)  in  Tempera-
each  case  27rf2/K.     Hence  in  the  case  of  glass  the  heat      ture-
thus  absorbed  during  charging  is  about  two-thirds  of
the  work  done  in  charging.
NOTE. — An  account  of  the  determinations  of  specific  inductive  capa-
city made  by  Schiller  by  the  method  of  electrical  oscillations  will  be
found  in  Volume  II.
K   K   *2


APPENDIX.
NOTE.
Recommendations  of  the  Paris  Congress  and  the  British  Association
as  to  Practical  Electrical  Units.
At  the  meeting  of  the  Electrical  Congress  held  in  Paris  in
1884,  it  was  decided  to  adopt  for  the  present,  as  practical  unit  of
resistance,  a  resistance  equal  to  that  of  a  uniform  column  of
mercury  one  square  millimetre  in  section,  106  centimetres  in
length,  and  throughout  at  the  temperature  0°  C.  The  mercury
column  thus  specified  expressed  approximately  and  in  round
numbers  the  value  of  the  ohm  according  to  the  latest  and  most
accurate  experiments.  It  was  resolved  to  give  this  unit  the
name  Legal  Ohm.
The  Congress  also  arrived  at  certain  conclusions  regarding  the
practical  units  of  current,  electromotive  force,  quantity  of
electricity,  and  electrostatic  capacity,  as  follows  : —

(1)  That  the  unit  of  current  should  be  called  the  Ampere,  and
be  defined  as  ^  of  a  C.G.S.  electromagnetic  unit  of  current.
(2)  That  the  Volt  or  practical  unit  of  electromotive  force,  or
difference  of  potentials,  should  be  defined  as  the  electromotive
force  required  to  maintain  a  current  of  one  ampere  through  a
resistance  of  one  ohm.
