222         M.  E.  Edlund's  Researches  on  the  Electromotive 
Zinc- Silver, 
The  observations  were  made  at  intervals  of  15  minutes. 
Exp.  39.  Intensity  of  the  current  =  tan  39°. 
Deviations. 
0-85 
0-93 
1-00 
Mean     .     .     0'93 
Eor  an  intensity  =  tan  45°  we  obtain  ^=1*15. 
The  passage  of  the  positive  current  from  silver  to  zinc  pro- 
duced a  cooling  at  the  point  of  contact.  Thus,  from  the  last 
two  experiments,  at  should  be  =  0*24  for  the  combination  of 
zinc  and  copper. 
Palladium-Platinum . 
I  soldered  these  two  metals  together  in  the  supposition  that 
the  electromotive  force  between  them  would  be  less  than  that 
between  palladium  and  any  one  of  the  metals  previously  inves- 
tigated. As,  however,  the  length  of  palladium  wire  at  my  dis- 
posal was  only  enough  for  one  of  the  copper  cylinders,  I  put  into 
the  other  a  platinum  wire  only.  I  considered  that  the  incon- 
veniences resulting  from  slight  variations  in  the  intensity  of  the 
current  could  be  more  easily  avoided  if  the  current  could  traverse 
the  two  cylinders  in  wires  offering  nearly  the  same  resistance, 
than  if  it  only  passed  through  one  of  the  cylinders.  From  what 
precedes,  it  is  evident  that,  when  there  only  exists  a  point  of 
soldering  in  one  of  the  cylinders,  the  deviation  can  only  attain 
to  half  what  it  is  when  in  each  cylinder  there  is  a  point  of  sol- 
dering, of  which  one  becomes  heated  while  the  other  is  cooled. 
The  result  must  therefore  be  multiplied  by  2  to  make  it  compa- 
rable with  the  preceding  ones. 
Exp.  40.  Intensity  of  the  current  =  tan  18°  15'. 
Deviations. 
7-53 
9-35 
Mean     .     .     8*44 
The  intensity  not  being  particularly  great,  the  deviation  may 
be  regarded  as  proportional  to  it,  whence  we  obtain,  for  intensity 
=  tan  45°,  -  =  25*60,  and  consequently  a  =  51*20. 
The  passage  of  the  positive  current  from  palladium  to  platinum 
induced  a  cooling  at  the  point  of  soldering. 
If,  with  respect  to  the  metallic  combinations  for  which  «  and 
ul  have  been  determined,  we  compare  one  of  these  two  quantities 
with  the  other,  we  find  that,  on  the  average,  ot  =  l'42ar     We 
