2  Prof.  W.  Weber  on  Electricity  in  relation  to 
velopment  of  the  equations  of  motion  of  two  electrical  particles 
subjected  only  to  their  mutual  action.  Albeit  this  development 
does  not  lead  directly  to  any  comparisons  or  exact  control  by 
reference  to  existing  experience  (on  whicb  account  it  has  hitherto 
received  little  attention),  it  nevertheless  leads  to  various  results 
which  appear  to  be  of  importance  as  furnishing  clues  for  the  in- 
vestigation of  the  molecular  conditions  and  motions  of  bodies 
which  have  acquired  such  special  significance  in  relation  to  Che- 
mistry and  the  theory  of  Heat,  and  to  offer  to  further  investiga- 
tion interesting  relations  in  these  still  obscure  regions. 
On  the  Relation  between  the  Laws  of  Electricity  and 
the  Principle  of  the  Conservation  of  Energy. 
1.  Electrical  Particles  and  Electrical  Masses. 
Particles  of  positive  and  of  negative  electricity  are  denoted  by 
the  same  letters,  for  instance  by  e  or  e'  &c,  but  a  positive  or  a 
negative  value  is  assigned  toeore'...  according  to  whether  it 
represents  a  particle  of  the  positive  or  of  the  negative  fluid. 
If  the  measurable  force  of  repulsion  exerted  by  the  first  par- 
ticle e  upon  another  exactly  equal  particle  e  at  the  constant 
measurable  distance  r  be  denoted  by/,  and  also  the  measurable 
force  of  repulsion  exerted  by  the  second  particle  e'  upon  another 
exactly  equal  particle  e'}  at  the  same  distance  r,  be  denoted  by 
/,  then  ±r\//  is  taken  as  the  measure  of  e,  and  ±r\Zf  as  the 
measure  of  e',  where  the  upper  or  the  lower  sign  is  to  be  taken 
according  to  whether  the  particle  is  a  particle  of  positive  or  of 
negative  fluid.  The  unit  of  force  which  is  here  adopted  for  the 
measurement  of /and/'  is  the  unit  recognized  in  Mechanics, 
namely  the  force  which,  when  it  acts  upon  the  unit  of  mass  re- 
cognized in  Mechanics  (1  milligramme),  imparts  to  this  mass 
unit  of  velocity  in  unit  of  time.  The  repulsive  force'of  the  two 
particles  e,  e\  so  long  as  their  distance  r  remains  unchanged,  is, 
in  acccordance  with  the  electrostatical  law, 
rr 
A  negative  value  of  this  expression  denotes  attractive  force. 
In  this  mode  of  denoting  particles  of  the  electric  fluids,  how- 
ever, e,  e'  have  not  the  signification  of  masses  in  the  mechanical 
sense,  as  appears  from  the  simple  consideration  that  e,  J  may 
have  at  one  time  positive  and  at  another  time  negative  values; 
but  nevertheless  the  values  of  ey  e'  are  closely  related  to  the 
masses  of  the  particles.  For  if  we  denote  the  masses  of  the  par- 
ticles e}  e'  (in  the  mechanical  sense,  according  to  which  the  unit 
of  mass  [1  milligramme]  is  determined  by  the  mass  of  one  pon- 
derable body,  and  different  masses  are  compared  with  each  other 
